Tha gap was huge when I came here. Now it is not so big and if anything I would say it's cheaper in UK than in Poland. During last visit I found out that fuel was cheaper here, bread, eggs, milk too
I prefer Romania for now because I earn well enough, and things are still cheap compared to Western Europe. The only reason I'd move is if some far right party got into power or to catch more concerts.
Obviously there are exceptions. And some countries, including Germany, are trying to snipe highly educated immigrants, which would of course earn decent wages. But not everybody falls into that category.