SI,
If you're including Duxford, then you ought to include Old Warden as well. Be aware though, that if you want to go on a flying day, you need to book a slot well in advance to ensure that there's parking space for you.
Old Sarum is also worth a visit - you can walk from the airfield to the fort, which is well worth an afternoon's exploring.
There are plenty of airfields within about 1 hour of Wycombe: just draw a circle 75nm diameter centered on Wycombe. If you stretch to 1.25 to 1.5 hrs then you can get to Le Touquet or even the Channel Islands.
Since you're flying 172s from Wycombe I assume you're a member of the Air Centre, so we may well run into each other (I'll be there this Sunday).
Brooklands