Having once owned a shiny new 1990 Miati, in blue, I thought I should chime in. Add a good sound system, upgrade the speakers if they already haven't. The stock is good but a CD player is mandatory!
Someone mentioned unzipping the back window before putting the top down. Sorry, but this is the manufacturers recommendation. I had some damage to my backwindow due to a problem when the alarm installer decided to put the top down for more room to work...
Some damage to the back window can be taken out by warming with a hair dryer on low.
Best advice, find a nice twisty road (having lived in England I know you have them handy) and go for it!
Bob