Constitution, themed groups & legal liability

We at the Southwell Area Transition Initiative (SWAT) have a constitution for our steering group, and have spawned two themed groups, one on energy (which is now an independent stand-alone organisation about to become an IPS) and one on food (which has just started and still exists on the coat-tails of the steering group).

One of our members recently raised some significant questions about legal liability. Our constitution (for the steering group) is quite loose - it doesn't name individual ,members, has no entry and exit rules for members and also envelopes the themed groups in its wording. The major concern is that as an Unincorporated Association (the legal status of a voluntary group) members of the steering group seem to be unprotected in terms of legal liability for any actions carried out either by the steering group itself, or by one of the themed groups which may (admittedly in rare cases) lead to legal action. For example, recently at a local Fun Day we had some cycle-powered equipment (music system, water fountain and smoothie maker) which was operated by members of the public. Whilst we had done a risk assessment beforehand, and were covered by insurance taken out by the organisers of the Fun Day, it still left us individually exposed to being sued for negligence (eg) if a child had been injured by one of the cycle machines.

My question is how have other transition groups, faced with a similar situation to ours (eg a steering group with a written constitution, and semi-independent themed groups) handled the liability question ? Have they taken out individual liability insurance, have they adopted a water-tight constitution, or something else entirely??

The member who raised the question in our group has been tasked with defining amendments to our constitution which would help, but it's not clear that this is enough!!

All comments and help welcome!!