Donington is a great circuit, and is an easy circuit to learn which Craner Curves being a great feature and the corner where you will probably need to practice the most. Its quite a fast circuit.
Oulton Park is very techincal but also a fast circuit, but only because it has a mixture of everything; decent straights, chicans, banked hairpins, steep drops and climbs etc. Its quite hard on the brakes here if its dry as there are at least 4 or 5 places where you are around 100mph and nned to slow down.
Anglesey is very short and techincal with very little straights but is on the edge of nowhere for most people.