Semy, from a long term wheelie bin user, I cannot for the life of me see how your council can justify emptying the brown bins once a fortnight. My family consists of 2 adults and 2 children and my bin is slightly larger than average (not sure how many different size bins the councils supply, but I know there is a tiny one for single users, average size for families and one slightly bigger (but not much) than average)).
My brown bin is always, if not virtually full every week! I would not accept having it emptied once a fortnight. My (average size) green bin is generaly full after a week and half and I always end up having to ram the contents down inside (which ultimately means it never gets emptied properly).
In the summer months, if the brown bin is only emptied once a fortnight, your peeps will find that they will probably not be able to close the lid properly and then all sorts of nasty smells and visitors will accompany that little problem. Perhaps you oughta to have a word with your local council and suggest they reconsider and empty browns once a week.
Please don't panic, and feel your business is about to go down the pan. You may feel you have weeks where you are not bringing in enough cash to keep you going (I know I have been there with my dom cleaning business, and indeed I am having a quiet time at the mo), but you do have regular customers, and you could use this 'quiet time' to think about other directions and getting out there and putting yourself about!
The council would be fools to think they could only 'get away' with giving fornightly brown bin cleans, so it will be a case of hanging on in there until they can sort their acts out (typical council idea of trying to save money, which most likely will backfire on them eventually).
It's not likely you could justify offering a green bin clean more than once a month as they just don't need it. What sort of cleaning system do you use? Could you use it to offer any other type of cleans. I know one of the bins cleaning companies in my area use (or at lease use to use) a pressure washer type of system, which I would have thought could be adapted to pressure wash exterior stonework!!
It's just an idea!
Jan