Shireena Marlboro I went to Ab Fabs near Heathrow. It's a large venue, with things like a dungeon, dark room, glory holes, disco and swimming pool (no swimming costume required!). It's just been refurbished, and is still having work done on it.
Don't be (too) nervous. You are in charge of things. Most people are very friendly, and respectful, (but watch out for the dreaded "towel zombies"), and understand that no means no.
Ladies generally turn up in something lacy, or tight (including pvc), but have a change of clothes with them for when things get, er
steamy...
As with any "casual" thing, make sure you know your boundaries, and stick to them!
If I can answer anything else, feel free to pm me, and I'll help where I can.