Locked out and will not start - alarm sounds off

If the microswitch is the problem confusing things, then the best you can do is diconnect the multiplug from that part (door lock actuator for example). In that way you eliminated that microswitch is making problem. 

However if the problem persist then problem is elswhere. 

To do continuity test you would need to unplug connector from 5AS. However, what TA22GT suggested, maybe it would be good to check other things which can confuse alarm box, like boot switch, bonnet switch and passanger door microswitch. Usualy we start with what we disturbed, but it might be that completely other thing happened in the same time making this confusion.

Regarding engine not starting, I would check that connections to starter motor are firm and good. Dimming lights without ra-ta-ta-ta sound might point to bad contact on starter motor.

To clarify 
After removing the door panel but before removing anything else I attempted to start the engine.
Later I attempted to start the engine with the door latch/lock mechanism disconnected, and subsequently with a spare connected.

My perception is that the more attempts to start the engine were made the sooner or the greater the probability that the horn would sound became a reality and the chattering activity also became more apparent.

The battery (disconnected yesterday before starting to charge it up) is taking more than I expected to get the green light on the charger and a green bubble in the battery spy glass. I have now put it on a charger capable of delivering a higher rate of charge.

One question regarding attempting to start with the door open or closed. Without the multi pin plugs connected to the lock mechanism the associated control unit will be “confused”. Im searching for a wiring schematic for that but of the three associated micros switches they do not all have the same starting point such as all closed or all open. So the control unit will be receiving “mixed messages”.Surely that therefore needs a locking assembly in place?

The other pointer is this. Operation of the key in the lock should overcome the lock closed situation regardless of super lock or not, and it didn’t and I think I probably tried that with and without the battery connected. So something is not right in the mechanism or with the set up of the drop arm from the key barrel lever arm to the door lock. The elastomeric insert around that rod as it locates in the key arm hole is tired and possibly or probably dropped out of position. But as it locked the car it was doing its design intended action for lock but perhaps not unlock.

I see the logic in disconnecting the last thing connected but I’d be interested to know and understand how the 5AS views the potential confusion with micro switches out of synch. I image it wants to see 2 open and 1 closed or vice versa but 3 open circuit would potentially be conflicting and adding to the problem.
Thoughts please

From what l have just experienced I suspect the battery is failing.
The trickle charger after about 18 hours didn’t seem to be making much improvement. So after about 2 hours with a more powerful charger I re connected the battery.
An instant alarm as you would expect, and probably greater decibels than yesterday.
So gave it go, and thankfully it started without any further issues. 
Whilst I don’t believe it solves the door lock issue it has at least enabled me to move the car to the garage to fit another lock assembly for trial.

Thank you Roverlike the likely clue was in the dash panel dimming.

Very pleased you are making progress.
Let's hope the door lock solves the rest of the problems.
Good luck.

Reflecting on this event two things come to mind an explanation of the electronic logic would be appreciated if it is known.

First: What is happening when the lock button is bouncing rapidly up and down and the door remains locked. Which switch and which aspect of the control logic is failing to work as intended?

Second: the recent experience appears to confirm the theory that as the battery voltage falls the alarm is triggered. Is that a known fact within the logic? In the past and particularly in winter when the temperature falls overnight I have been woken with the car alarm sounding for no obvious reason (the car was in the garage). In those early days of ownership the car was locked using the fob/blipper. Since then it has been locked using the key. I believe it is a known condition that battery voltage falls with temperature if only slightly. Any logical explanation for the alarm to sound other than locking with the key excludes the volumetric sensor.

One thing needs to be cleared first: one out of three swithes does not have open or close state - it has changeover state, meaning it is closed in one position or closed in the other position. That particular switch is responsible for opening or closing the door (it is called sill-up/sill-down).

Answer to your fist question is that particular switch in door actuator is playing up, making the door sill to come up and down. Because of that quick action door does not have time to cycle from open to close, so it remains closed.

Second answer is that when alarm is within armed state by the fob, any tempering with car battery will triger the alarm. Of course if you disconnect the car battery you will silence the alarm, but as soon as you connect it again alarm will sound. If you lock with the key, seems you are not activating this feature (however this needs to be confirmed yet). 

So, if your car battery at one moment goes that low looking like it is disconnected, and after some time it gains capacity again just as you connected it again, alarm will sound if you locked your car with the fob.

Well after some brief relief yesterday after gaining access I started to test the spare mechanism that I intended to fit. By manually operating the external levers I could confirm that the micro switches were doing what they should.
Getting this mechanism back in place can be trying to say the least and so it proved.
Once fitted and without joining the loom connectors I gaily closed the door. Bother, or words to that effect. At least I had had the sense to open the window before closing the door.
Would the door open no it would not. Now my experience when I dismantled one of these locks suggested that operating the key should override and locked condition whether that be key locked, fob locked, or super locked. But this time the key would not do that even if I leant in and added some more force on the rod.
In for a penny in for a £ and with nothing else to try I connected the battery (the horn is temporarily disconnected). By operating the fob a few times to lock and unlock the doors it eventually enabled me to open the door but with a lot of whirring that I expect was super lock and it’s clutch.

I then connected the battery charger to the battery and operated the fob several times without any observed issues. I had the door open and the lock cheated by closing it with a thin screwdriver. 
Next I put the battery condition instrument on the battery (with everything disconnected) it gave an 80% charge reading which I thought was ok .
The green ball was just about visible yesterday evening and overnight the trickle charger made no improvement on that.

So why is the key not overriding the locked condition?
Why would the potential better battery voltage stop the whirring nonsense?

Yes I always lock with the key to avoid any possibility of the internal sensor etc triggering the alarm. I might use the fob and potentially super locked condition if parking in a busy major city. As I live in a very quiet rural location I don’t want anything disturbing the neighbours.

The question regarding the alarm was to do with “state of charge” if left for a period of time and the battery volts drop will that give a condition where the system thinks it is being “attacked” and sound the alarm when in reality it is just a collapse in battery voltage?

 
 This is a diagram that I came across some time ago and regrettably cant recall or find the reference to the author. I think it came from a MGF.de website.
I tested my most recent installed mechanism and it behaved as this - or at least it appeared to behave like this to me.

I believe this diagram is off Dieters website. This website is a must for any enthusiast, it overflows with information, it lists the original monochrome circuit diagram if the f; it make an interesting comparison with the later edition.
M

Regarding the origin of the wiring sketch. Yes, that seems to ring a bell in the memory.
Hopefully someone (perhaps Roverlike or anyone else) well versed in the electronics of these cars can add some further explanation regarding the issues Im experiencing with these locks.
Im very puzzled why the manual key could not overwhelm the system with or without the battery connected, but thankfully once the battery charger was connected and that presumably boosted voltage the fob operated the system.
 

It's strange but I have never once locked the car with the key. Just the fob.
I better try it tomorrow.

Modern switch mode battery chargers are pretty hopeless at charging a battery that has discharged beyond a certain state. What voltage is the battery showing after it has been left (without a charger connected) for 3 or 4 hours ?