Your budget will get you a nice 748 or 996. Just be patient.
My choice would be the 996 every time, purely because it has the engine size that allows it to be ridden in a less frantic manner if you want to.
theres a wide choice of 996, the early ones up to end of 1999 with three spokes, gold frames and no nitrided showas.
2000 onwards with five spoke wheels, silver frames and nitrided showas.
You might even find a 996s within your budget, a bit better engine with a bit more power and usually a single seat.
If you could stretch to a few more £££ go for a 998, much better engine that is still used in the current 999, but you are looking at nearer to £6,000 than £5,000.
Having said all that a 748 is a good machine, just be aware that an R will cost a bit more to run as it should have belts every 6,000 miles/12 months.
www.ducati.com has the specs of older bikes and a comparison function
Ray