My fave are Iceland, Slovenia and Montenegro. All have amazing natural beauty and are less touristy as most other countries. And I just love architecture of Ljubljana. Podgorica in Montenegro can be missed though, it's nothing special. Just visit the coast and natural beauties.
Try Germany Italy France Spain Greece Croatia Poland Russia Sweden maybe also parts of Romania and also UK
Spain
If you're in the UK, technically you're already in Europe.
Ireland uk France italy and Spain are nice