Thanks for the response...
The garage is adamant they've double checked everything (I've been in this game 20 years and we wouldn't have done anything stupid was the response) and are even trying to charge me an extra £100 for an auto electrician, even though they've not got the thing running yet.
I have seen postings relating to the ECU and key chips needing to be re-paired for the imobiliser if the ECU is changed, but the've not changed the ECU, it's still the original one so it will still be paired with the key.
They did say the auto electrician has said the engine will only run with the ECU that was in the scrapped car the replacement engine came from. But I don't see how this can be the case, are all the ECUs and engines totally unique? Surely the replacement engine will run with the original ECU unless there's some fundamental difference between the two engines?
From what I've been able to piece together from various places, the two engines I have, given the engine numbers, are pretty much the same and only manufactured about 5 months apart. I could just do with someone being able to confirm this and that the replacement engine will work with the original ECU in the car.
Cheers...