There's not really any more to this than meets the eye.

I didn't threaten anything - I was merely asking for _advice_ on how to
fit an integrated slimline dishwasher into a kitchen which I _had_
bought from B&Q. I fully understand that they are not obliged to offer
advice, but to my mind knowledge and a helpful attitude are what set
good stores apart from the rest. I also fully understand that this
lady knows nothing about DIY, but that's not why I'd been taken along
to speak to her. My points a

1) There are experienced staff in the store who are very helpful when
on duty - I'd been taken along to her by another staff member not
because of a dispute, but simply because he was not able to help and
could not find a member of kitchen showroom staff. He thought she
might be able to help / find the relevant staff member.
2) Rather than defer to someone who knew something, she waded in with
wholly inaccurate information on products - 500mm slimline dishwashers.
3) She refused, quite unreasonably in my view, to make any attempt to
find a member of kitchen showroom staff with whom to discuss my query
about a B&Q kitchen: bear in mind this store provides a kitchen
planning service.
4) No sympathy expected but I believe the relevance to uk.d-i-y is that
if someone is deciding on where to buy a kitchen, my experience may
sway their decision.