definately do it. i've done 4 so far. lydden hill was my first last october. it's a brilliant track and ideal for the sv even when you have so little power, i was managing to humble a number of more powerful bikes
only problem here is that they don't do many track days each year.
my second was at silverstone GP circuit. not ideal on a restricted bike, but it was imense fun and one of my favourites, but not ideally suited to the sv by the fact it's such a high speed track. again though if you have some nouse about you, you can do over many more powerful bikes in the corners. i can't wait to go back to this circuit on a full power bike.
next i did a driving day at raf northolt. only managed to get onto that a member here who works there. again a great day.
and most recently i did mallory park. i must admit that i didn't particularly enjoy this circuit (although i must admit i did crash (not badly)). i managed to get back out there and in my mind i had managed to forget the crash. i just didn't particularly enjoy the layout, which considering that it has some similarities with lydden i was surprised.
my 2 days at silverstone and mallory park were through hottrax. most places i think are ok with 33bhp licenses, but a quick e-mail to whichever company you use, will tell you if that rack won't allow you on.