Just to round this thread off - the issue was indeed to to with the GM5 module. There are limited places that will fix the window relays (loads that fix the central locking relays) and I was being quoted around £200 to fix.
I fitted a replacement GM5 module (thanks @enuff_zed) and that has sorted the issue. No recoding was needed - but I did have to re-pair my keys.
I fitted a replacement GM5 module (thanks @enuff_zed) and that has sorted the issue. No recoding was needed - but I did have to re-pair my keys.
