Stewart (Sunshine),
I once priced up a big posh hotel/golf club/fitness spar; it was really big and would've taken me and another window cleaner at least two days per week to get round it all within a month.
Anyway, we didn't get the job and I found out OCS were continuing to do the job at HALF the price we quoted.
Then I had the chance to do three big care homes and quoted a fair price for a high-quality job; and never got any of the jobs. Other window cleaners went in cheaper.
I asked here how this could be done.
I found out that on big jobs, you have to prioritise what needs cleaning, making public areas and the management offices number 1; then just checking the lesser priority stuff; missing them if they don't need doing.
Anyway, the guy who posted the advise received a bit of flak, but just stated that this was common practice for big jobs on a budget.
But it sounds like common-sense to me.
In future, when asked to do a big job I really want, I'll go in with a low quote and do a shoddy job. If I get sacked, I've lost nothing, but with a bit of common-sense; I bet I can still keep the job and still make it profitable to me.