Anyone who says they have to send their children off to be abused at weird boarding schools, and so cannot afford to live, is an idiot,
You might call them idiots, perhaps because you can't understand them, but some people do actually put their children first. I know one couple who sold their house and bought one less than half the size in order to keep paying the school fees.
In Poland its 11k PLN gross .
Where in Poland and on what basis would you be employed? That would net to about 9,000zl per month which will get you a much better standard of living than £35,000 in London. A decent one-bedroom flat in a good part of most cities in Poland is going to be about 1,800zl a month, so 20% of your net salary. In London you're looking at £1,500, so more than 50% of your net salary. Monthly travel pass in London can be over £300 a month depending on what zones you want (although it'll probably be more like £200), in Warsaw I pay 202zl net for a 90-day travel pass.