This was an old post, Well the garage that changed my box never worked on my car since. I changed the sensor (cant rememb er how much it was from either Pulsarbobby or Mr GTiR) and still got the same problems, so I just took the fuse out.
Got my gearbox changed AGAIN recently by Olly Owen, and strangely enough putting the fuse back in, the ABS now works. I havent actually asked Olly if he noticed anything unplugged apart from that he noticed a few bolts missing from the gearbox, an engine mount loose, and another bolt grinded off.
Next time any major work needs doing its going back to Olly as at least I know the job was done properly.
Have you checked the connection in the engine bay for the front left ABS Sensor, I think its by the air filter.
Ill try to find out for you if Olly noticed anything unconnected when changing the box which could have effected the ABS Sensor