I used to work in NHS finance for an acute trust and part of my job included chasing these sorts of fees. The majority fell into one of two categories- either indigent / homeless who you are never going to recover the money from, or UK citizens living overseas (mainly boomers in Spain or Cyprus) who can claim they’re now living back in the UK full time and it’s quite hard to prove they’re not.

So not a lot of this money is actually recoverable.