is it still possible to use either a Polsat box or NC+ box in England
Yes, it's possible. Many Polish watch Polish channels in the UK using sat sets brought from Poland. If you bring a tuner from Poland, connect it to any satellite aerial directed into a proper satellite (it's possible that the dish in the UK has to be bigger than in Poland, but I don't know), then it will receive Polish TV.
It's against the regulations of the operators (nc+/Polsat Cyfrowy), but they don't do anything with it, because there is many subscribers who pay them only because it's the only way of receiving Polish TV abroad.