Quote: BTW, would a £80 flatbed (Canon, say) that comes with slide/negative adapters, allow better results than the Peak service?
Pass ... I think it depends a lot on how well exposed the negs are. Dense negs are hard to scan, I'd guess the professional scanners would do a better job.
I have little experience with scanning (colour) negs but in my experience the cheap(ish) flatbed scanners are disappointing, the resolution is fine but they have difficulty coping with contrasty trannies compared with proper film scanners. You should be able to get a secondhand film scanner off eBay for not much more than £80 and I think it would most likely do a better job.