Hello Mr C
A guy at work bought rgv250, althought it was sitting around for a number of years in a garage and although in good nick, he has had endless problems with the carbs, and trying to get it ticking over correctly, and as a result has not got it running for over a year. (But I think its more to do wil time to work on it) But he said something about Stan Stevens is your man for tunning. And he has bought and sold bits on this site. maybe of some use.
http://www.rgv250.co.uk/ good luck
regards
TopiToo