Thanks for your replies..

Yes I mean the complete handbrake module/cable unit..

Customer has phone to see if I can fit a 2nd hand unit..but I said I wouldn't of thought it would work once programmed to another car..

So he has fitted it and it make a slight noise when switch operates..but doesn't lock wheels...he drove it to me for a diagnostics..but I can't get comms with the unit...
But I get comms with old unit..
So I told he to go on his way and fit a new one.....
Why do they think it's my problem now he's 2nd hand part doesn't work?
Case closed