Many charities for those suffering from disabilities or medical conditions carry a link to this broker (Able2Travel) on their websites:
http://www.ch-travelcare.co.uk/
I posted that link for someone a few weeks ago and they kindly took the time to post a reply, stating that Able2Travel had provided by far the lowest quote that they'd found.
However, on another thread, someone recently posted to say that (for their particular needs) MIA had provided a better quote than Able2Travel could:
http://tinyurl.com/lwuzv7
Age Concern's own travel insurance might be worth a look:
http://www.ageconcern.org.uk/AgeConcern/travel _insurance.asp
InTune might also be able to provide a reasonable quote. (The company is wholly-owned by the charity, Help the Aged):
http://www.helptheaged.org.uk/en-gb/OnlineShop /Insurance/Travel+insurance/
Many people find Saga to be relatively expensive but they might still be worth trying:
http://www.saga.co.uk/insurance/travel-insuran ce/
(They can't be expensive for everyone. They provide my motoring insurance for a tiny fraction of the quotes offered by most other insurers!).
Chris