Hmm... I don't know England well so when you say south-west England, I assume you mean around Plymouth. but I believe there is a BDSM group in Hampshire... a little far but it may be in your interest to have a holiday or something there. It's called the 'South Downs Munch Yahoo Group' and it's held on the 2nd Sunday every month, at 1pm. (Along with the thursday after sometimes) They have around (or just over) 200 members.
There's also a friendly one in Surrey, which is run by Mistress Ayla. (I think... don't trust me on that one!) It's called Epsom Deviants.
Those are your closest and best bets as there aren't many 'major' events going on in your area. Of course, there may be smaller local ones that haven't had as much publicity. My suggestion is that you start talking to people you know that are into kink, and maybe they happen to know of some places near you.