was it a quote or a receipt for the work done? i would be suspicious until i had seen the second one.
working in a bodyshop we get many requests for estimates/quotes for minor bumps in the hope of getting the other party to pay up then repair it themselves for a fraction of the costs and pocket the difference. But having said that it doesnt take much damage to get up to £795.00 worth of repairs, something that isnt always evident on 1st inspection.
The other option is to threaten to get your insurance involved , thats what you pay for, see what his reaction to this is.