If he was only on the next street AND you already knew him then I would agree that a different expectation could be considered.
However, in that were the case then I am surprised that he quoted such a high price.
On the other hand if you just went round to his house after seeing his van then he may not have liked that. Many people with sign written vans expect to be able to live without people knocking on their doors at all times for help/free advice! He may have quoted high to put you off.
Nor do I think that you should bargain with him over an inflated price. He quoted that price and it should be the lowest that he is prepared to do the work for. ( Unless he is an Arab who expects to always be knocked down on price ).
My view is that its an apparently excessive price. That might be that he is a bit of a cowboy. OR, and thats perhaps evidenced by him not coming twice, that he expected that you were only asking with to intention of doing it yourself.
Alternatively he may well be employed and does not want to do jobs outside his job or just wants to spend the evening at home and does not want other work. I know a mechanic who had to move out of London to avoid neighbours wanting him to work on their cars all day long.
I cannot come to any judgement as I dont have enough information but I strongly suggest that you get someone else who is an independent to quote for the supply and installation of the part. Should be about £84 plus the part.
Tony