Hi mate, yea Ive been on one at snetterton
it was brilliant, have a look here
if you want to see a few vids.
Donald's another member on here who is building a track car, have a look at his thread
there are some vids of his track day at knockhill in there somewhere
TBH you don't need to make any modifications to go on a track day, you can just turn up in a completely standard car and go on track (just make sure you're brakes and tires are in good nick
if you do any mod's i would recommend getting the car to handle better first by upgrading the brakes, suspension, reducing weight, tires etc.
and then move on to getting more power
when i was on track the main problem i had was being chucked out of the seat on the corners, and since i got some decent seats and harnesses theres a hell of a difference
I would swear they have improved my driving.
i did try to organize a track day last year on the forum but it didn't happen in the end
But i will be trying again this year