I had a look while I was writing the Ops manual
. It's used by some places as a perfectly legal protection for liability insurance in a building, by others as a revenue builder. We've found it's better for us to operate as a FTO & RTF with public liability insurance in place and no questions about how/when/where/who. It's not a CAA requirement that RTFs have clubs - rather it's a requirement that clubs have a RTF to be able to conduct training for licenses/ratings themselves, eg Sleap, or have an attached RTF that does the flying training, eg HFS/HAC. A few clubs have given up on the expense and have become purely social clubs, with small discounts available at the local non-club RTF for members.