If it's a camera malfunction, get a replacement and pickup where you left off. Cheaper than £90 x 30 disks. ... £2700????? Tell him to go #*&!#.
Maybe he deals with professionals, and you sound like you're just a family man with some home videos.
For him to not suggest several affordable alternatives right off the top of his head (which I'm sure he can do) tells me he's a thief.
If you go elsewhere that does the same business and find them honest people, I suggest that you tell your story of the £90 per disk nonsense, and mention his name. You may save innocent others from being taken in by him.