I route I use for some advanced training taking in some rural 50s then pushing onto some really nuice rural nationals. Points of interest along the way:
Avebury - Some lovely bends, a nice pub and some big stones. Well worth going through twice.
Hackpen White Horse, Alton Barnes White Horse and the Uffington White Hourse
Wantage - Couple of nice cafes there for a brew
Mostly B roads to get you working hard. The Wantage to Swindon rd past the Uffington White horse is brilliant
A fast and twisty route to Swindon, just have to watch the road surface as there's pot holes a plenty near Wantage and risk of gravel and manure on the roads. All leading to a nice challenge if you're winding ot on a bit.
Some decent country road riding. A fair new 50's but you can generally get a lick on. Lots of scope for over takes. Flowing rollorcoaster roads between Upton and Streatly
Fast A roads from Didcot to the A404 near Maidenhead with the only sticking point is the traffic in Henley, though thats mainly through commuting time.
If you're going the opposit way there's sometimes a speed camera van at the top of the dual carriage way out of Henley. It's national speed limit droppin to a 40 for about 1/4 of a mile.