Newbie from Morecambe

It sounds like a job for a professional. I may rig up a red neck horn to get it through the MOT as the local auto electrician is busy till October.

This problem with the horn.  Have you been able to check the rotary coupler in the steering wheel?   There is a video on YouTube.

Many thanks for the link. I'll pop the wheel off and have a look.
The coupler wouldn't explain why the alarm sounds as soon as I lock the car. I assumed the horn not working and the alarm sounding where linked ?

Hi Airportable, is it's the part numbered 67 on this drawing that you are referring to?
 

Yes that’s the monkey. They’re a sod to get out & you have to be methodical, don’t just pull once you have the fixing hardware removed.
This job was the first “technical” job I did having just bought it. It had a long MOT & absolutely no chance of passing one if I were to have offered it up for test on the day money changed hands; the horn was just one failure point.
As I have mentioned I have recommended changing this unit to others, with varying degrees of success, it was however the fault on mine with no shadow of a doubt. They were buttons when I bought my replacement, as with all parts, “The only way it up”.
Bitz’ is in all probability your best bet.
M

Speedg99 wrote:

Many thanks for the link. I'll pop the wheel off and have a look.
The coupler wouldn't explain why the alarm sounds as soon as I lock the car. I assumed the horn not working and the alarm sounding where linked ?

 Ah!  I wasn't fully understanding the complexity of the problem.  The alarm is sounded with the horns so my logic was that if the horns themselves work and the fuse is OK the rotary coupler was possibly faulty.  I had thought that the alarm sounding when you lock the car might have been the sort of blipping that car alarms used to make all the time when they were armed.  In my '04 TF, there is a fair bit it clicking and the hazard lights do a bit of flashing when I set the alarm.

I’ve managed to pull up a circuit diagram & although it’s a bit, no, it’s a lot of a squint, if the horn honks with the alarm, then the relay in the multifunction unit must be closed. This implies a circuit from the fuse, through the relay in the MFU, allowing the voltage enabled by the alarm to sound the horn.
The horn buttons are in parallel with the alarm & so the clock spring assembly should be checked.
You have a meter, set it to continuity & with one end to ground & the other to the header 0288 (K109), press the horn button & you should get a reading of the spring is working.
I can’t help you with the header whereabouts, I’m still on holiday & working on my phone!
M

I have a spare MFU,  You are welcome to borrow it to try if you cover my postage.

Update 
firstly, Notanumber thank you for the offer but id already ordered one from MGFNMGTFBITZ.

it arrived and I've fitted it. In the process I've found i can bend like a contortionist, ouch! 

When i plug in the horns and blip the alarm it doesn't go off any more result!

..... however still no horn off the steering wheel button still. Ive checked the coupler and i don't think I'm getting continuity through it. So I'll order one. 

in the process I've snapped off a tab from the tiny horn button mounted in the steering wheel which is a swine.

This little car is really testing me!!
I'm starting to think this car has had a life of issues as many bolt heads and screw heads are mashed up. Dodgy twisted wires etc. It's only been owned by my god parents who would not of touched a spanner, it makes me think a rough garage has done this. 

   
 

Keep at it, your doing fine. Your car is going on for thirty years old & it is thus a survivor.
They aren’t the easiest car to work on & in certain cases the “less talented” spanner jockey was given the jobs, such was the paucity of respect our little cars engendered.
I know of a number of instances where this has happened with less respected cars & with absolutely certainty.
Legend has it that MG Rover had a part number for a pain reliever gel which was to be applied after certain jobs on our cars.
M

HONK HONK!!!
We have a horn.
The red box behind the dash sorted my alarm and the squib ring / horn coupler sorted the horn on the steering wheel.
thank you all for your guidance on this. I'd have never in a million years found these fixed
Very happy.
MOT on Thursday 🤞

Good work