My discovery 2 is immobilised, it cranks, but no starts, im getting communication problems with my ecu all continuity is fine, so im no believing my bcu is dead, or dying, can I code a new one myself with a nanocom, if so how, please.

 

No, you cannot. You will need to get a new matched pair or you'll need to find somebody with an old test book machine and have them code or replacement BCU for you.

 

I have the same issue, crank no spark or power to fuel pump. I have a matched pair of ecu & bcu from a donor. If fitted will the car now start?

 

No way to know, sounds like you have not diagnosed fully yet.

 

The car was running fine, battery died overnight, swapped with new battery, car refuses to start.

 

Again, you haven't diagnosed anything. Highly unlikely you need a new bcu. More likely it was locked when battery died, now it is in security mode. Try locking and unlocking the door with the key fob or key three times. Or do a search, tons of post on this.