"Getting funding for research is extremely difficult," says Anne Carter, head of appeals and publicity at the Tuberous Sclerosis Association.
"From the donors' point of view, they can see research as a big black pit they are throwing money into and getting no result."
Julie Greenfield, research projects manager at Ataxia UK, another small disability organisation that includes some medical research alongside its support work, agrees. "It is not easy to get money from trusts for research projects," she says.
By definition, scientific research can't be quantified in the same way as many other projects - it might lead to a major breakthrough, or it may just prove that a particular option is a dead end. The TSA has had some successes, most notably a recent grant of £120,000 from the James Tudor Foundation. But this has been possible only because the money is earmarked for clinical trials of a drug that could result in the first treatment for tuberous sclerosis tumours and which could in turn be used for treating cancers. "The reaction from funders has been interesting - we've had serious donations, larger than we'd normally expect," says a TSA spokeswoman.
Funders don't usually have the prospect of seeing this kind of return.
"Research is a very slow process," says Elaine Ingram, marketing manager at the Arthritis Research Campaign. "Most of our projects average a three-year cycle, then lead on to something else - 90 per cent of the time you're not able to report back with fantastic success. And it's not always easy to translate research results into a layperson's terms."
Another issue, explains Ingram, is that funding is often retrospective, in the sense that the project has already been identified and the organisation has agreed to fund it. This rules out lottery funding.
Ingram says there is "nothing earth-shattering" about the way she handles trust income. "We're always honest," she says. "Most people understand that they are funding the research, not the result. Sometimes a project even has to come to a standstill, and you can't hide that."
Carter says: "When my daughter was a baby, doctors told us that most children with this condition die in childhood. There was no research until we set up the first programmes. Now we're on the brink of a cure."