Let me see; you have , in effect, 136 windows plus the shop front windows at the bottom.
The job is a one off; is there no chance you can secure a regular clean???
Who's going to keep it clean in the future???
If you really can't secure a regular clean, and it's really dirty as you say, I reckon we'd charge something in the region of £100/150.
Obviously it would be easier if I were stood in front of the place to view it myself but that figure will give you something to start with.
Good luck!!