If you work in a sparsely populated area then that's why you object to £15 for that job, because time is money. Some would object to that price in some parts of the country is busy cities, where you could spend your time in traffic jams. Again time is money. It is not unusual to have a weeks work all within a mile or two of houses like that. In this instance I would do them all day long at that price, but if I had a ten minute drive to the next one than I would make the customer pay for that time, pushing the price up by at least 25%.