Well here is an example for any expats who require health services in the UK, it is my personal experience and is not a made up story.
I emigrated from England in 1970, lived in Australia for thirty five years then moved to Thailand in 2005, only returning to England for an occasional holiday. So I had been away from the UK for forty two years.
Last year (2011) I was involved in a motorcycle accident, the costs of hospital treatment and a lawyer cost me 500,000 Thai baht. Three months after leaving hospital I had a heart problem and was told the cost of my operation in Thailand would be 800,000 Thai baht. It was to replace a heart valve and repair another. I never had that kind of money so decided to write to the National Health Service in England to ask what my position would be regarding medical treatment in the UK. They said if I was returning to the UK to live I could get any treatment I required as I was a British citizen, but I would need to acquire a new National Health number from a GP in the UK.
I booked a one way ticket to England, stayed with my sister, registered her address as mine with the Pensions Department and got a new National Health number. I had my heart operation, which was free, as was my medication. I admit going through the health system in the UK takes time and I was six months waiting for the operation. I am now back in Thailand after seven months in England. So as you can see it is possible for expats to get free hospital and medical treatment in the UK no matter how long they are away from the place. I hope this has helped any expat from the UK who might need hospital or medical treatment and does not have the money for it here in Thailand.