Sorry Joe, I didnt mean to snap.

Thanks for the advice. In future I will add more detail to my posts. I often find on forums people are ready to pick at points rather than offer advice. I jumped to the conclusion this is what you were doing, in my defence I had been up since half 3 and hadnt had a coffee.
I often find on forums people who dont want to answer the question as they think it is stupid still waste thier time and mine to put a flippant comment, so I already had my backup in defence, waiting for the onslaught. The main reason for forums is people asking for advice from people who may have already been in that situation. There are obviously many variables but I am interested in seeing what the others have done in a similair situation. I am not expecting the perfect answer just seeing what the genaral feeling on this is.
The property is an old victorian hospital that has been refurbished a few years ago for business units. It has never been cleaned and this years bout of snow has pushed the carpets to thier limits. We have discussed with the client that they need to be maintained once the initial clean has taken place but often advice falls on deaf ears when more cost is involved, even when I explain the cost of replacing the carpets would be 5 figures.
Anyways in answer to some of your questions:
My business partner and I will be doing the cleaning to make sure standards are maintained, and so we know no corners are being cut.
There are windows all along the building so access is pretty easy, only a few areas will have to be on portable and those areas are generally better as they are the least walked areas.
The friend of ours has the final say on who he picks for the job, as long he as feels we are not taking the p we have the job. He has asked us to price as usual. The price is 4 figures at our usual rate, so I wanted to see if people offer discount on huge volume or charge as per usual. The only reason we are asking as this is the largest job we have quoted (and we have done some huge jobs)There is plenty of profit in that figure to account for it taking a day or two longer than we predict.
I do know how to price a job I was just interested in seeing how others would tackle it. The site took us half a day just to measure up and on initial inspection is a very daunting site.