Plus the NHS is essentially run by immigrants... 26% of doctors are non-British (and many more 2nd or 3rd generation immigrants). Your main problem is not having any way of keeping track of people in the first place, no compulsory identity cards or need to register where you live... So planning any public services is more or less a guess. And if you want to be up to no good, con people, abuse the system it is really easy (compared to most other EU countries) only due to that, immigrant or Brit, nothing to do with foreigners.