There are loads.
Isis in newcastle, Antac, Clearview in london, and so on. Its a bigger industry than most people realise imo.
A couple of years ago, the MyHome plc group started window cleaning (domestic houses, not commercial) with a fleet of very smart looking vans, I was a little worried about the prospects for us little guys.
Soon after, they de-listed from the stock exchange and must have sold their window cleaning section (or just shut it down) and I've heard nothing about them and window cleaning since.
Can't say I'm not highly relieved.