I think everyone should visit London, and see some of the famous sights.
There can't be anywhere more beautiful than Snowdonia in Autumn
There are so many gorgeous beaches and stretches of coastline, but as you've done a lot of that, then are you looking for something different ?
History - Bath, Chester, York, Stratford
Hills / Walking / Scenery - Lake District, Yorkshire Dales, Peak District, Snowdonia, Brecon, maye some of the long Distance Paths ?
Do a tour of the Great Cathedrals and that will take you into some beautiful Cities
Huge amount of heritage and social History to be found in some of the great Cities - Birmingham, Liverpool, Cardiff, Sheffield, Bath, Bristol, but also places such as Ironbridge, or the Black Country Museum
Architecture (as well as Cathedrals and most of the Historically interesting places) - Cambridge, Oxford, Bath