This little gem from GW recently caused a stir:
"We do no demographic research, we have no focus groups, we do not ask the market what it wants."
However for those interested in such things the WSS recently did their Survey. Only a few details have been released so far, IIRC it'll be detailed in issue 75 I think.

Heres the bits theyve revealed so far.
link
Link2
link3l

Certainly some interesting stuff. I think we'd all have expected Scifi in general (and 40k in particular) to be the most popular genre a few years ago...I'd have still expected it to be slightly ahead but it looks like FOW and BA have taken the lead. Im surprised Medieval was more popular than Napoleonics as a period, even with saga.

I am surprised by the age groups that are prevalent. Part 1 suggests the uk gaming scene is quite young, but Im 31 and most of my gaming group is at least a few years older than that if not nearly double that age, so the "youth" aspect isnt as apparent to me.

Its difficult to draw conclusions before the rest of the info is out, and with nothing else to compare it to other than anecdotal evidence, but as ( as far as Im aware) its all weve got to go on I thought it aught to be worth a look.