In the UK sex is still some what some thing you do behind closed doors and should not be discussed openly. You could argue that TV programmes and films are now quite graphic regarding sex and nudeness which is true they are, however overall it is seen as some thing not to be openly talked about. When compared to parts of Europe sex shops and sex toys are something you talk about with a partner, or if single you keep it quiet.
Amsterdam for example, the subject of sex and sex toys is "So Seventies" As with Denmark, Germany etc. I can not envisage walking past a chocolate shop here and seeing chocolate shaped in the form of a penis, where as in Denmark I have done.
I think that relates to how we have percieved sex over the years, it eneded up being-Outside of the bedroom- sordid and tacky, a place where "dirty old men" went to get some form of gratification, Soho for example. Some of you may well not recall how that place was many moons ago. "Got some under the counter mags if youre interested" Type thing.
The UK has changed it's attitude towards sex a great deal over the year's, I do think companies like LH-No I do not work for them-Have helped that change. For example here we are talking about masturbation, albeit in an annonymous form, but it is a change, a change that takes sex away from being seen as seedy and tacky.
A group of friends of mine, male and female, went to Amsterdam. We all went to a live sex show, there was a man and a women both naked on stage and they had sex. The way they had sex? it could not have been less tacky than if some guy had of been walking around in a full on spacesuit saying look at my willy! They had sex, but they did it in a dance form, music played they had sex in a choregraphed fashion. It was to say the least enternaining.
Now that all said and in answer to the OP question, yes there are groups that will meet and masturbate together, but they are mainly swingers not just entuasts of masturbation. You can go to places and masturbate, but it will be you and, well, just men watching, all very well if you like that sort of thing. As to a group of like minded people as you mentioned, extremely rare. Rare as in there is a mixture of people dicussing such a topic.
Bringing us back to LH, is it so nice to come to a forum and be able to talk about such topics in a way that you ladies, will not get harrassed to watch a cam, sent rude pics ect. Whereby a conversation can be kept "Normal" If that word even exists :)
Apologise for the long post to your question.