I find when quoting an ad hoc job they usually pan out at some obscure figure, £9, 11, 13, or even £10 or whatever, thats when i base it on the number of windows, etc. Problem i have is when i do a semi for say a tenner and they recommend me to their neighbour, relative etc, who has a 'similar' sized house and they tell them the price, sometimes its spot on and the same ,others they have a massive porch, or more side windows etc..so you end up like Richy says..the ten pound window cleaner !! Whether you like it or not !!