Basically, anything Georgian. The architects of that period had the most sublime taste and sense of proportion. Stamford, in Lincolnshire, is a Georgian gem (and quite a few others - like Bath, of course, which I am not so familiar with). But my favourite Georgian buildings of all are here in Manchester, where I live. There are little pockets of Georgian loveliness among all the horrible Victorian/20th - 21st century 'clutter'. My favourite is a little row of shops/workshops on Port Street in the Northern Quarter. Just ordinary vernacular buildings but gorgeous - and they have recently been quite tastefully restored.