I was tempted to try the DIY method myself but I view this more as archiving so I want the output to be the highest possible quality. I think I'd probably rather pay someone to just get it done! Plus they can clean it up etc. So long as it isn't too much. £100 ish sounds reasonable.
These guys look the best (best website!) of those I have briefly looked at:
http://www.transferhouse.co.uk/
Plus they are just around the corner from where I work. Crucially they don't seem to be tied to transferring only to DVD. I think I'll get them to just give me some 1080p mp4 files. That way I can back up online. Safer than keeping the DVD in a drawer somewhere.
Unless anyone comes back with horror stories I'll probably give them a go.
It would be interesting to do a DIY version and compare the outputs.