That is complete nonsense, there is no way to erase an ecu memory that is more likely to damage it if there is any residual voltage left in the capacitors within the ecu, I suggest anything you do now is just causing more problems, it my be time to call in the professionals. Sorry to be brutal but MGF is a fairly modern car and the old ways of flashing alternator/ dynamos have long gone, to check faults now you really need diagnostic tools.
Just to interject, I concur that as with most of the MGF and continuing to the TF, the majority of components are a continuation from inception. The early would only refer to it being MK1 F, there are no lights associated with the alam other than the round LED the symbol on the lock (without checking) could be the "E" mark which could look similar to the "epas" indication on the cluster, also as far as the "machine gun" sound I also have had this and yes it can be a sign of impending failure of the locking mechanism but also common when the battery voltage is low, I have also heard from others but not experienced the "alarm sounding on ignition switch on" when battery voltage is low maybe something to check and at very least eliminate, should the replacement lock or battery charge fix the issue I'm afraid its pscan/T4 time as a lot of time can be wasted best guessing the fault.
The only way to disable the alarm/immobiliser is Via the EKA Code, you do this via the drivers door lock with a code lock 3 unlock 2 lock 1 unlock 3 etc specific to your car, if you don't have this code then you need someone with a Pscan or T4 to interrogate the control unit, I cant help you with this, maybe someone local(ish) has one who can help, alternately give a call to MG Mobile Mechanics on 07595 708278 or Rough luck racing (Mobile Mechanics) 07766 993717 they can advise better than me, Id be more than happy to come over and help with anything else if you need it just private message me, hope that helps, I do know a very good Mechanic too but you may need to get it to him, he is in Aston Fields MBM Engineering Mark Brooks 01527 575390, hope this is helpful.
I think you need those connected as they connect to the door switches it sounds like you have a fault with the alarm module, have you got the EKA code to disable the alarm (I suspect not) but that would help.