A RX-8 is ideal as it loves to be thrashed, cheap, and the handling is superb. It's got a lot of the mod cons I like and touch wood is relatively reliable with good compression figures.
Last year I went to the following tracks
Castle Combe again
I have another track day booked later this year for Oulton Park and want to do one in the summer possibly castle Combe or Bedford.
Modification wise I have kept it as stock as possible, I have added yellow stuff pads with c hook discs, de cat with pro drive exhaust system and got a good set of federal 595 rsr and some vredestein ultrac vorti for normal and wet weather. Maintenance is easy and cheap and well as pre mixing with 2 stroke oil. I have also had a mini map which adds a cold rev limit, ups the oil pump as well as the rev limit to 9750 as well as a few other tweaks.