I've done two of these full unit cleans in the past, one was 100' x about 50' charged £1600 for and it took about 4 days with pressure washer and extendable lance, one man. The other was slightly smaller 80' x 50' but had windows and atruim so less cladding, that was done with wfp over a weekend and charged £800. Both jobs were blue chip companies, so had a little more of a budget to play with. I would say that if this is a weekend job for a smaller company charge £600 for two men??