You must have seen the packs of sweating keenies bouncing across the Commons whilst being yelled at by short haired men in army fatigues. My five year old son thinks they're wonderful and we've heard pretty good things from the people who've attended. One question - what do the instructors carry in those rucksacks? I told my son a magazine and sandwiches but I'm not certain!

http://www.britmilfit.com/

And this is a deeplink to their locations:

http://www.britmilfit.com/locations.aspx