The wording of the current Ride Leaders handbook is open to interpretation
as allowing ride leaders to insist upon helmets within the letter of Cycling UK policy.
IMO that would be a deliberate misinterpretation but it's not my opinion that you have to worry about.
Well I had a look at the discussion forum for the group, and there were some quite strong words expressed
"Even if you do not value your own life, I would urge you to show consideration to your ride leader who is responsible for all, and your fellow riders who might well be traumatised by witnessing a serious accident involving one of their riding friends. "
"I acknowledge that such respect and consideration is present within the grade 4's, where I am one of the ride leaders, and where it is the expectation of all that fellow riders will wear helmets at all times. "
"I should stress that this is a personal view, albeit from an experienced ride leader, but I know that it is shared by the vast majority of other ride leaders within the group. If you doubt that, please talk to them. "
and a reply from another group leader
"You offer no cogent argument for not protecting yourself by using a helmet; the argument about primary or secondary safety is irrelevant. I see the UK Cycling stance as political rather than safety related. My personal experience has shown the value of a helmet and the experience of others has reinforced that value. Do what you want but don't ride with me."
(btw this discussion was in the context of a helmeted rider suffering a concussion.)
So anyway, I have cancelled my CUK direct debit as I had no idea I was distressing people with my lack-of-a-helmet.
(incidentally nobody (including myself I should add) seems to object to the consumption of alcohol on group rides.)