Based on the NHS site, you are entitled to free healthcare if you are an ordinary resident in the UK. But it can happen that you are still denied free healthcare (if they believe you are not an ordinary resident), in which case you have to pay upfront before they start your treatement, and you have to try to claim your money back.
Unfortunately the steps to do this are not really documented on the NHS websites. Searching on google for topics related to NHS refunds only result in issues regarding dental and optical care, as they are not (usually) free for patients.
Does anyone know what steps are needed to be taken to sort this thing out?