Check out the Kings Arms pub on Poland Street in Soho. It is the popular Bear bar in Soho. http://www.kingsarms-london.com/ The local bear group Bear Hug meets there http://www.bearhug.net/ They have a link to the bear clubs in London

The weekend you are in town is Bear Pride UK. http://bearpride.co.uk/

It is also a Bank Holiday weekend so there will be lots of partying going on. As for what to wear just be comfortable. So jeans or shorts are fine. T shirts, shirts rugby shirts are all fine too. In fact you will look like most of the others about too.

A good whats on guide is "BOYZ". They have an online version too: http://www.boyz.co.uk/

I'd have offered to take you out for a pint but I am off to Chicago and Seattle myself on May 22nd. PM me if you want to ask any more questions