What to see btw here and Kent!

[Frith2013]

I’ll be travelling between Evesham and Kent (nr Dungeness) next week.

I won’t be driving on the motorways so will be on the A40 over the Cotswolds.

I’m stopping halfway at the YH at Holmbury St Mary’s in Surrey.

Can anyone suggest something free (or nearly free!) to see on the way?

Thank you.

Painshill Park
Reigate Hill and Gatton Park
Runnymede
Riverhill Himalayan Gardens
Sevenoaks Wildlife Reserve