Thanks for all the suggestions, many I've not thought of.
I've got big pain in the thumbs (osteo arthritis) so my solution is:
1.Scallop your fingerboard. You will then require less pressure to cleanly fret the string - makes a huge difference.
2. Low,low action. Better to sacrifice tone than to not play at all.
3. Thomastic KR116 flat wound stings for classical guitar (can still use a magnetic pickup)- Smooth, low tension, easy to play.
4. Use chords incorporating open strings.
5. Open tunings.
6. Low Stress Diet: eat nothing from the cow and give up wheat; obviously stimulants like tea, coffee, alcohol and cigarettes don't help (if you're like me and can't give them up then try to not be a glutton. reduce your input of these things)
7. Take zinc, magnesium, fish oil and selenium supplements.
8. Attitude: do what you can, while you can, and be grateful that you can. Best wishes and make as much music as you can.