My wife is from a very comfortable middle class Polish family and went to one of the best universities in Poland. In her summer holiday before starting university she worked in a factory in the UK for minimum wage assembling car headlights. She did this because the pound-złoty exchange rate made this work more financially rewarding than anything she could have done in Poland.

I have more examples of Poles who are working in the UK right now, simply because of the exchange rate.

I've met many UK-based Poles and not one has preferred life in the UK to life in Poland.

If anything, the exchange rate allows someone in the Polish bottom 10% to climb out of that 10% much more easily than a bottom 10% Frenchman could: Go to western Europe and work for the minimum wage for ten years. Upon their return they'll have more than enough for a nice house.