The UK isn't cheap or the rest of Europe expensive when you live in each country. Prices in the UK haven't gone down or prices in Europe gone up loads. The prices here have gone up a lot here, especially over the last 3 years, but instead of things going up a few pence like it used to, it's been 10, 15, 20 or even up to 40/50p on some things! It's just that the £ to the Euro rate dropped a lot 3 1/2 years ago and has never regained, so it's only when you travel to Europe, convert your cash and buy things that you'll get stung and get less value than you used to. Of course it will be the opposite for when anyone in mainland Europe comes here to buy as it will be better value once they have converted their cash than over there.
Why the £ has never risen to like the 1.3-1.4 Euro's to the £ like it used to be given how badly many countries in the Euro are doing such as Greece, Italy, Portugal, Spain and Ireland beats me!