I can relate to the always bringing of ones own water bottle, whenever i am in a situation where snacks / drinks are offered, all the questions starts popping into my head: "What if i dont like it" "What if i make too much noise opening it" "what if i spill" etc etc, and i end up declining, politely at first but sometimes people just keep offering, i know they do it out of politeness but still..
Anyways, Id just like to say that i think you're a very brave person Gawain for going out there in the first place, but that support group sounds like it might suffer a bit from having been just the same group of people for a long time, if you can go back there then thats great, but if it ends up being too daunting a task then i hope you wont give up on the concept of support groups all together based on a single bad experience.
Social cues suck, because they are based on experience as well as the unwritten rules, so the same cue might prompt two completely different reactions in two different groups, so how do you know which response is appropriate at a specific situation?
If you find out, please share!