I think a 600 should be fine for you then, it wont be too bad on insurance and its not super fast like the 1000's are, but a 600 isnt to be laughed at, they say these days people only have 1000's just to say they have one, in reality on a sunday ride a 600 will be perfectly adequate for 99.9% of riders
There are the main sports 600's:
Honda CBR600 (F and RR)
Suzuki GSX-R600
Kawazaki ZX-6
Yamaha R6
They are the main ones, a fair few other less common brads also make them, triumph etc.
In my opinion all of the above bikes would be fine for you, its just a case of looking at which ones you think look the best and which you are comfortable on, for £2500 you can get yourself a good condition model of any of them. Mileage, overall condition, any addicents etc are all big factors in the price as well.
You are looking at ~100bhp for most of the ones I said, and at 190 odd kg the power to weight ratio is pretty impressive, 500bhp/tonne isnt bad at all.
As you have a while to think about it I'd suggest looking for reviews on them and find common faults on each, if the bike has been looked after properly and serviced regularly then they should be fine. Go and have a sit on them too, get a feel for the different riding positions, although they all look like they would be the same there are lots of differences when you actualy get on one.
I hope this is of some help to you.