£1 a window is fine on domestics but you will need to drop a long way from that when you have all the glass next to each other. You could do that front face in an hour or a bit more maybe if you're plodding. Maybe the trees will slow you down a bit. Assuming there are no access or other hidden issues, three hours would be the very top whack to knock that out on maintenance cleans. First clean would undoubtedly be longer though. I'm referring to outsides only. I know some will say this is too low but to be competitive, £150 would be OK if you're happy with turning over £50 an hour on maintenance cleans.