There are literally thousands of great places to visit in the UK, here are a few of my favourites:
Belfast - See where Titanic was built
Liverpool - Birthplace of the Beatles
Edinburgh - The castle is fantastic
York - History around every corner
London - Where do I start?
Manchester - Great nightlife
Bath - Visit the famous Roman baths
Windermere - The fabulous Lake District
Avebury - A mystical stone circle surrounds this village
Hadrians Wall - Lots of Roman stuff, Houseteads Fort, Vindolanda, Chesters Fort
Whitby & Robin Hoods Bay
Ben Nevis
etc.......