That doesn't mean he's not a good mechanic, there's not many people I trust with my cars! I won't bore you with why I know he's up there among the best.
I just like to provide oil that is recommended by owners, and as the spark plugs are available cheaper here I would rather provide my own and save what he would charge as full retail plus his mark-up. He told me the plugs would be about £15 quid each plus VAT, so £72. I can provide them for half price, and we won't argue over any warranty on spark plugs or oil, I wouldn't be worried anyway.
I appreciate what your saying though, any proper 'parts' would be supplied by him.