Warning: track days are damaging to your bank account and are severely addictive.......but dam good fun.
I'd recommend try before you buy, trackdays are different to Supercar days at Nutts Corner. I have no affiliation to Creative Motorsport but I'd recommend you rent one of their cars for a track day to see how you get on before committing to the expense of a track car.
I mentioned it in the members car thread that Pablo has about his Mini Cooper track car. I booked Creative Motorsport's Mini Cooper in June for the wife to drive at a Trackskills day. She loved it and so did I.
Sounds like a plan - I absolutely love going karting and drag racing so doing a proper track day would be fantastic fun I think and as you said, try before you buy.