Never been but would love to go to Guernsey, Alderney, Isle of Man, Orkney and Shetland, Isle of Skye, Cairngorms.
Haven't been to and not fussed about visiting (sorry!) Suffolk, Bedfordshire, Lincolnshire, Northern Ireland.
Would absolutely recommend Edinburgh, Glasgow, Fort William, Newcastle, the countryside around it into what I call "the empty north", the Lake District (travel by train and hire a car there), Snowdonia/Eyri, the north west cities, the Peak district, Cornwall, Devon, Exmoor, Bath, London, Brighton, South Downs, Arundel, Jersey and Sark. Dorset is a real place and a lot of it is stunningly beautiful, the countryside inland is quieter than the coast. Also some lovely canals (there is a channel 4 programme about canal boat life which is strangely soothingly addictive).
If you are visiting Wiltshire OP, see how many white horses you can spot (chalk ones on hills)