A few companies do them - MSVT, Javelin etc. I've done three with MSVT (although not yet in the 86) at Brands and Bedford Aerodrome, they're quiet good and reasonably priced. If its your first time see if you can book a novice track day as a normal day allows professional racing drivers on the track and they can be a bit intimidating.
You will need to buy or hire a helmet, put your towing eye in the front (I bought a second one to put in the rear of the car as well) and pass a decibel test but if your car is stock that's not an issue. You get a class safety briefing before the session starts.
Most track days offer tuition with a professional sitting beside you for a few laps so you know the racing line, breaking points etc - well worth the extra as you can get the most out of the car, especially if the track is new to you. Just book it when you book the day
Insurance is the big one - do you take it out or not? Depends on your attitude to risk (I was going to say skill level but no matter how good you are you'll never stop 'all the gear and no idea' man in his £1k Citroen Saxo crashing into you). Its expensive but with the value of these cars probably worth it. I had a £7k car when I done my track days and insured it for the first one but didn't bother for the next two.
It's a great day, I'm sure you'll enjoy it
