They're not legal tender anywhere, including in Scotland. Obviously, they're widely accepted in Scotland, and while banks will typically accept them in England (especially the ones based in Edinburgh!) most shops won't.
As well as the hassle, the other reason for saying no is that you don't know what real ones look like, so it would be easier to give you fakes or otherwise invalid ones.
Hmm, bit late now to say 'go and change them at a bank'. Up to you, but I'd take (some of his) time to compare them to some images online, check for watermarks, metallic strips etc. You can dress it up as 'Oooh, aren't these interesting' if you like.