Have read whole thread!
Feel it's only fair to tell you about the "other" side of M&S. Only because I can see why the OP would want to complain, loudly, about her experience, but people very rarely say if they've had a positive experience. Given that, I feel I should. So:
I'd just moved to our new house and was out fetching something or other and fell over in the street.
It was a bad fall and I partially broke it with my hand, which swelled up and I couldn't move my fingers.
I was very shocked and in a weird, disoriented and very shocked state, i wandered into the local M & S.
The security guard took me off to a little room, called for the first-aid trained person (they have one in every store, apparently,), who came and checked my wrist/fingers weren't broken. She then made me sit there, and went off to get me something to drink, while the shock wore off. And no, she didn't charge me/wouldn't accept payment. She even offered to 'phone for a taxi to get me home! (Which I declined - by that time, the shock was wearing off and I was feeling a bit silly).
And I wasn't well-dressed - I looked very scruffy and grubby.
So, the OP had a very unpleasant experience but I don't think you should extrapolate their whole customer service ethos from that.
Agree bananagate sounds a bit heavy-handed.