Great Malvern has a lovely character and setting (like the town).
Sheffield Midland has been superbly renovated, great sandstone structure with long, wide platforms; interesting water feature outside.
A swan between two very ugly ducklings (Derby and Leeds).
Huddersfield, Lancaster, Stirling all feel "grand".
Some of the forgotten east coast stations have retained a lot of character (eg Saltburn, Bridlington, Filey and Beverley), unlike their drab west coast counterparts (eg Southport, Blackpool, Morecambe, Llandudno).
After a grand tour recently I was surprised how many stations in the south west looked very run down (Exeter St Davids, Plymouth etc).