I don’t know what has been covered by RS, but my suggestions would be
France - Venise Verte - stay in/near Coulon. Meander on a boat trip or hire a bike and cycle around the canals in France’s answer to Venice (but without the price tag or the crowds). Gorgeous stone houses surrounded by fragrant flowers. Pretty villages aplenty.
Ile de Re just off the coast of La Rochelle for plentiful oysters and twee villages and just south of there, the island of Oleron for a less touristy experience.
England - the stunning Northumberland coast.
Rutland - like the Cotswolds but without the tourists.
The Isle of Wight - as England was 50 years ago.
The Isle of Man as you won’t meet anyone else who has ever been there! Avoid during the TT races, as it will be busy.
Scotland - Dumfries and Galloway for beautiful rolling countryside and stunning bays.
The Ardnamurchan Peninsula- one of the most stunning parts of Scotland.
Spain.
The stunning Picos de Europa in northern Spain.
The Caceres/Trujillo/Merida/Badajoz area for castles, Roman aqueducts and historical centres.
Canary Islands - Fuerteventura for an almost lunar landscape in parts. La Gomera for away from it all peace.