Late reply... I did go and I enjoyed it, thanks. Did you go yet? It was fun and I'd likely go again.
Simple format. Pay on the door (around £10), or I think you can buy in adavance. You get changed/strip down in a side cloakroom, place your bags in a provided bag to be left with the staff behind the counter. They were friendly and helpful. I wore my boxers and trainers. I'd say 50/50 split between those who were naked or in underwear. Hard to say on the numbers as people would come and go... maybe around 50-60 guys when I went? Felt like a good amount for the space.
The venue has a few distinct areas with several cabins/cubicles and dark corners. Most people seemed to switch between two areas. It got fairly busy in one room, plenty of touching, mutual wanking etc. Although it's billed as no sex, there was some more action going but this was tucked away in the dark corners, and away from the main areas. It didn't bother me.
Later on, just about everyone had moved to an area with bench seating running around the edge and porn playing on the screen. The room was pretty full. Although I didn't see or hear many guys cumming early on, quite a few were blowing their loads by now! Occasionally when you could hear that a guy was obviously close to climax, some of the crowd would quickly move in to watch. It was quite fun to see/hear that
It was a good mix of people. Everyone was laid back and I didn't see any pushy types. It seemed that some were regulars and quite familiar with each other in the bar area, being socialable, chatting about all sorts and catching up with each other. I'm quite shy, so didn't chat too much with others. I wish I was a bit more outgoinging on that front! However, the majority weren't really chatting and just there for the touching and wanking fun. I was probably there for about 2hrs, around 7-9pm by which time the crowd started to thin out.
I recommend it and hope to go again soon.