Sorry for what you are going through. Yeah, it would over whelm me, too. Can you escape to another part of the UK until the Olympics is over? Or perhaps on the weekends at least, if you have a job?
As for all the tourists sitting everywhere, have pity on them. They are sitting because they are tired from all the walking, and constantly bucking the crowds of other tourists and natives. They are probably hot, too.
I'm not into attending big functions any more. Besides being uncomfortable in crowds, I have bladder and bowel problems, and don't want to be far from a bathroom for long. I also don't want to have to wait in line to get to use it. By the time I head for the facilities it's too late for standing in line outside. AAAAAHHHHH!! !! !
I will occasionally go to the nearest Walmart for both foods and non-foods (it is also a big grocery store), but they have a pair of large, multi stall rest rooms up front, AND another pair of large, multi stall rest rooms out back. The pair in front are busier, so sometimes there is a little line standing, but the pair in back gets less use, so no line standing. I use the ladies room out back, of course.
I really think you need to get far away from the maddening crowd for the duration of the Olympics, or at least on the weekends.