If your transponder battery dies (and it will eventually). A guy called Ricky Chadwick can strip 'em down and fit a new one. I had my one fixed and he did a superb job. He's a shed load cheaper than sending them back to AMB, plus he's a racer, so the money goes in the right pocket.
Phone him on 07710 032898 or email on Rickychadwick@aol.com