ok. i do a building similar to this, although my job also has a porch of which i do the inside.....i also do about 20 windows on the inside....i do th job every 6 months, and it took me 4 hrs on the first clean...(filthy) ... the next clean will take me 3 hours... i cgarged £230.
if it was monthly i could charge £130, but then i would be able to do it in about 2 hrs 30 mins.
i live about 5 mins away....