Hi Adrian, I've tendered for a number of schools and similar contracts and to my knowledge there aren't any courses to help complete such tenders.
(Prochem, being suppliers to the carpet cleaning industry, will not cover this sort of thing in their courses.)
Is the information you are seeking along the lines of all the policies (Environmental, Health & Safety, Equal Opportunities, Staffing, Training etc) or more to do with the calculating of hours required etc?
If it's the latter I suggest you obtain a copy of BICSc Best Value productivity figures.
If it's the former maybe you could ask the organisation responsible for submitting the tenders for some help.
With tenders there is no substitute for experience so maybe if you don't win any of the schools this time around you could treat it as part of the 'learning curve'.
Congratulations on your business, it certainly seems that you are heading in the right direction.