I took my petrol mower in to be serviced and have the blade sharpened, but when I went to collect it I was presented with a bill for £120, which is more than the mower is worth. When I refused to pay he kept the machine and is threatening to sell it in order to recover his money.
In the absence of a specific agreement a tradesman can charge a reasonable amount in other words the sum a similar firm would charge for the work. If he won’t accept less and you want your mower back you may have to pay his bill, but insist on a receipt that lists the work he carried out; then if you get a couple of quotes from other firms for the work you could, if you wished, sue him for the difference in the small claims court.