That's a good list freddo - I'd definitely recommend York as many have said - it's a very compact slice of English history and architecture all in one city, and not too far from the beautiful Yorkshire Dales to the west, or the nice coastline of Whitby and Scarborough to the east.
Also enjoyed Dublin - not too over-powering of a city like London, but very friendly people and lots to see, especially if you can get out to the beautiful countryside.
The north west of Scotland is also pretty, but then I would be a bit biased to that, seeing as it's where I currently live