According to its latest magazine, NGO members can buy legal expenses cover as a bolt-on for an extra £27.50. No idea if it is any good, as insurance cos tend to wriggle out of anything they can. But the NGO itself is a sound org and will always do its best.
For a non-org route, look at Country Cover "Club", or C3, the trading name of Country Cover Limited, which is touted by some on this forum as an alternative. This is an "introducer", operating out of a terraced house in a village in Northamptonshire, with £75k in net assets and, as far as I can see, no employees, according to Companies House. This "introducer" (most biz seems to be introduced to a firm of which one of its two directors is MD) offers "legal expenses cover". This is actually administered by Legal Insurance Management Limited (or was, until July). On inspection, the master policy states such claims will be entertained "If you can convince us that there are reasonable prospects of being successful in your claim..." Good luck with that!