Having got a problem with the alarm which has decided to not release the immobiliser could be one of 3 things. The alarm module, the immobiliser module or the main engine relay.
Thought i would start with the alarm module located in the boot but according to B&G is no longer available. I searched the product code in case it was used on other cars and found one on ebay saying it fits both the Metro and RV8. If it is correct then a possible source of replacement alarm ecu’s.
I made an offer and when it arrived I fitted it, programmed / paired my spare remote button.
To programme a key fob see …… https://mgrv8.info/2024/09/05/mg-rv8-new-key-fob-programming/
It worked making all the right noises and flashes etc …… but did not release the immobiliser!!
So now I’ve got a spare alarm module.
MG RV8 info news and reviews 
I had the same problem so I have located the immobiliser module which is located under the dashboard in the centre above the clock I soldered the wiring and I can now go anywhere with confidence that it will start I’ve kept the bits so it can be reanstted if i sell it
LikeLike