If you go to Western Europe and say this, no one will ever believe you.
People in western Europe can't believe that many Poles only earn £300 a month either ;)
The weather is better in Poland
This I do agree with. London is far too warm in summer, and doesn't have proper winters. ;)
It means you can save ~36% of your salary per month. How much will you save in London?
Hmm.. let's see. This was what I was earning/paying in London 2 years ago. I've checked rents etc in the area I used to live in (and as I still travel there regularly, I'm aware of transport costs). My salary would have kept up with price rises.
Net salary: £2400-2500/month (varies according to unsocial hours payments)
Transport: about £75
That leaves about £1200-1350 a month disposble income. That is a LOT of money for a single person to have left each month, and explains why I used to take foreign holidays every 6th-7th week or so.
I imagine that your "friend" in Wroclaw wouldn't be able to do the same ;)
Unfortunately, I left that job (and London), so I earn a fair bit less now. This means I can only have six foreign holidays a year now :( waaaa. lol
So, it looks like I win. I could easily save 40-50% of my salary, and I didn't even have to live 10 to a room like a Pole to do it, I lived alone, lol. Only 15 minutes from central London, too :p