I did Biggin-Shoreham-Manston as a practice QXC with my instructor, but did Biggin-Norwich-Southend as the real thing. I think Shoreham and Manston is slightly easier, as there are more landmarks (a lot of Norfolk is fairly flat) and, if you're based at Biggin, you'll be more familiar with the area in general.
Canterbury (cathedral) and Ashford (stadium-like shopping centre) are very obvious and recognisable, and I flew over a chalk crown just east of Wye (I've never managed to find it again!
) There's also a reservoir/quarry with a conveyor belt (marked on the 1:500 000 chart), just north of Battle, which is very distinctive. Heathfield, with the radio mast, is easily recognisable too.
As the others say, try to relax and enjoy it - you'll feel a great sense of achievement afterwards!