Thanks everyone. I've done a bit of hunting around and no joy.
I'm working on rearranging all my finances to have all debt repaid within 5 years (bar mortgage). That means if I have to stop working because of RA or a related illness we'll only have the mortgage and bills to worry about. Bar my life insurance (which covers existing conditions) no other income related insurance will cover my RA, Meniere's or related illnesses. Seeing as RA has put me at risk of heart, lung, blood, stomach, eye etc ad infinitum conditions there's not really a lot left to insure.
I used to do legal work for insurance companies so I know how they weasel out of payments by any means necessary so I'm not necessarily surprised, just terribly disappointed that they still live in the dark ages regarding the treatment of this condition and how most people can lead normal working lives with the right medication. We're really not that great a risk any more and I would have thought they'd have moved with the times. Oh well.
I'm covered for death, accidental death, accidental disabiltiy. I'm just not covered for sickness or disability as result of sickness. That's the bit I have to cover from my own pocket.
I did have some advice over on Monesyavingexpert.com from an independent finance advisor who told me to go see a local IFA. He said cases like mine are not solveable over the internet and face to face advice could turn something up. I'll keep you up to date with what happens.
Thanks for the suggestions but I'm 4 years off being able to take advantage of any of those companies lol!