seems kind of low
Oh, I have no doubt that you're absolutely correct. I would imagine that the true number is many times the quoted 1500 figure, but even with this lowball number witness the "ho-hum, more scaremongering from BusHitler's lapdog PM Brown" posts at The Scotsman site.
It would certainly be interesting to set up a CCTV cam outside some of the mosques and see who goes in or out... hopefully that's being done but in this age of hysterical political correctness I'm not so sure that it is. Any agency that would be discovered doing something like that would be instantly pilloried as 'racist'.