Of course they have. Do you know why? Because a person who works labour can actually earn enough to carry a decent life on those greener pastures, while in Poland many people who do white collar jobs can't!
Not really - a person who does a physical job in the UK is often better off being unemployed. It's not an easy life, especially if they live somewhere expensive.
As for white collar jobs in Poland - the issue with this is often that they perceive themselves to be of a certain status and demand the status symbols to fit. They then drown under a mountain of debt. I've seen it happen to someone who was earning around 4k netto - not horrible money, but she bought a very nice flat and car, then struggled to live. If she'd bought within her means, she would be fine.
If you want to comapte ex-mining towns try to compare it with Katowice, Zabrze, Gliwice... how do they look comparing with English ex-mining towns?
Katowice is definitely better off, but I've never been to the others so can't comment fairly.
I think a more fair comparison would be as compared to the former eastern block countries.
Recent comparison I can make is with the Czech Republic. Prague is behind Warsaw, and there doesn't appear to be much construction going on (unlike in Poland). It certainly seems like the statistics are heavily skewed in Poland because of the existence of many poor small farmers - which didn't exist in Czechoslovakia. I'd actually say that Poland is developing faster these days - I really saw little sign of construction in Prague, and places like Nachod are absolutely horrible.