We have a window cleaner who comes to our estate (the Guinness Buildings on Snowsfields) who does a good job (he cleans the communal windows up to the 4th floor. His name is Chris and his number is 020 88579925
No problems, not sure how much he charges - I think he has a contract with the housing trust. I would be interested to find out though - It is getting a bit cold and windy to be leaning out of the window now
I think they probably list the costs under estate cleaning. They are about to change the cleaning contract, and there was talk about cleaning all the windows on the estate using a big hosepipe that could reach the top level (of course it never occurred to them that while they had the scaffolding up, they could have cleaned all the windows then.. but that would have been far too simple for Guinness I suppose).
For a cleaner, this may not help you much because I've never used this person. I just got a business card in the mail yesterday that I'm going to call. The name is Misha 07957540502. I hope she works out because I'm on my 3rd cleaner now!