I think I might've struck gold
Found someone selling a 'set' off a same year gti containing both door locks, boot lock, petrol cap, ignition barrel, one new style remote central locking key, transponder ring, and ecu
Forty five quid ... gotta be a bargain!
I believe I should just be able to swap everything over and bob's yer uncle, will need to get a spare made but that's a minor issue