I am not sure if i'm the only one who did not know this but if you go back to the UK for a visit and get sick you have to pay for a visit to the doctor, or any non emergency treatment and medication. Before leaving the UK I was told I would be able to get NHS treatment for 3 years at which point I would then have pay or prove I was a resident of UK again.
As I am currently in the UK and sick, I was suprised to find I had to pay £30 per doctors appointment + medication at cost. I do have full medical insurance I got with the credit card I booked my flights with and so can claim the money back but if I did not have that cover probably would not have taken out medical insurance for a trip to the UK as I did not think I needed it. You do need it !!! it could work out expensive.