A good few centuries worth of incredible history for a start!
Not everyone assumes a holiday is about sitting on a beach. Arts & Culture are a huge incentive for tourists to visit the UK. Luckily the majority of museums are indoors as are galleries, given the current inclement weather.
Not to mention shopping, sport, theatre and some pretty good restaurants to - and nobody does pageantry like we do, opening of Parliament, Queens birthday, I know friends from abroad who were in awe of out 2012 Olympics opeining ceremony.