From other users on here the ECUs are different but will run just not the best, depending on whether it's coilpacks and/or facelift engines there may be other engine compatibility issues.
If you swap like for like ie a 1.0 dizzy pre facelift for a 1.3 dizzy pre facelift you should be fine.
NATS (facelift and coilpacks?) means you can't easily swap over ECUs as they are a matched threesome (ECU, ignition reader, key fob)