Jon,
You might want to call the British Embassy and see if they can help you find a solution.
Your Embassy might also have connections within the British NHS that under the circumstances can bend a few rules that would let you get back to Great Britain for treatment ASAP.
Also there are a number of charitable foundations in GB that might be of some help such as MacMillian (
www.macmillian.org.uk ), but I suggest you see if your Embassy will coordinate this for you.