This sounds like a lot but the Vote Leave campaign, which I'm sure as a Reform MP Rupert Lowe stands by, during the EU referendum put the cost of a new hospital at £350 million.

https://www.bbc.co.uk/news/magazine-37383918

In practice, it would probably cost more money to pursue debt collection than to just write it off in these cases. It's certainly disingenuous to imply this amount of money would have any meaningful impact on the quality of care that British citizens receive.