Welcome.

I personally don't have first hand experience, so I can't help you. But
you might also consider posting the question to rec.scuba.locations and
uk.rec.scuba. Sharm El Sheikh is a popular destination for UK divers on
holiday.

Hi,
I came back from Sharm el Sheikh this Saturday (05/29) in fact. I
didn't go to Dahab. Apparently it is a more laid back type of place
then say Naama Bay. (one guide booklet calls Dahab the Egyptian
Kathmandu!) It is also cheaper shoppingwise but from what the local
DM's I talked to say the diving is not that great (the Blue Hole and
the Canyon being exceptions).
You will get better diving around Sharm el Sheikh (Ras Mohammed
National Park comes to mind) and cheaper T-shirts,  beach towels and
water pipes (hookahs) in Dahab.
Can't reall help with dive companies (just don't patronise dive ops
that cater to Russians) as there are so many and generally they are
segregated on geographical/linguistic lines (i.e. clubs for German
speakers, French speakers, Italian, English etc).
As Alan Street has already suggested try uk.rec.scuba as a fair amount
of Brits dive in Egypt.
John