A pprune search should find some good general advice from previous threads.
The most noteworthy thing I can think of for the Manston > Shoreham leg is to be aware of the large number of (hang) gliding sites along the Northern edge of the South Downs. Keep a very good lookout!
Also, bear in mind that if you route close to the coast the weather can be quite different either side of the downs. I was caught out on my QXC (Goodwood > Lydd) by low cloud blowing in from the sea. I back-tracked to the River Arun and followed it through the gap in the downs (to keep maximum clearance between the ground, me and the cloudbase). It was a beautiful sunny day again on the other side!
I maintain that the QXC was the most challenging / exciting / satisfying etc etc flight that I have done.
Try to relax and enjoy it.
TG.