I am trying to remember all the modules that require Dealer coding and I don't think the General Module is one of them.
Normally, it's only a relay on the module that are problem prone.
If your car is not under warranty you can have your GM5 fixed, but I don't know if they ship to the UK.
Try this site: http://www.bmwgm5.com/
Edit: Yes, you do have to have the dealer recode the box.