Arriva 37 Wycombe-Maidenhead: Cookham, Cookham Moor, Stanley Spencer Gallery (no need to pre-book).
Courtney 16/16A from Maidenhead: Bray, also short walk to River Thames.
Courtney 15 from Maidenhead: Thames Bridge at Maidenhead, Dorney Rowing Lake, Jubilee River, Dorney (for Dorney Court*), views of Windsor Castle from Eton Wick (also near Thames Path), Eton (cross the Windsor Bridge for Windsor).
White Bus 01: Windsor to Windsor Great Park, walk to the Copper Horse Monument (and the view from it), Savill Gardens and Virginia Water are also there but quite a long walk (White Bus 500 is better for those venues), Ascot.
First Berks X74: High Wycombe via M40 to Farnham Common for Burnham Beeches.
*Reopens in 2021.