I just don’t get the objection to him going back to his own country to get what he is entitled to. He lived, worked and payed his taxes in the UK for some time, his whole family lives, works and pays their taxes, if he gets well again I am sure he will eventually live and work in the UK again so he is not getting anything for free.
Further, the system there is what the system is, the people agreed to it, the government agreed to it and now he is asking them to live up to their end of the bargain. You can be damn sure if he owed the UK government or a local municipality something they would expect him to hand it over and probably imprison him if he didn’t.
By the way, the reverse does happen as well, US citizens who have lived abroad come home and make use of their medicare benefits because where they lived abroad had very poor or no health care system in place and I as a US tax payer am glad they do it if they need to.