As a Canadian living in the UK on a temporary work visa I get to vote (LOL THE QUEEN IS ON THE LOONIE), and am served by the NHS for emergency stuff but my visa says "no recourse to public funds" which I'm pretty sure means I don't get things like disability benefit.
Pensions on the other hand, I'm not sure about. I'm getting tax relief for my pension contributions, but maybe there will be a withholding tax if I leave without naturalising.