My friend is thinking about starting to play, and wants to start on acoustic (I play electric, so don't really have any advice on what guitar to get), so I was wondering if you could help?

He has a budget of around £80, but the cheaper the better (although not necessarily swapping quality for cheapness).

I'd ask in the acoustic & classical section, but around that price you can't go wrong with Alvarez, Epiphone, or Ibanez. They all make lower-end starter acoustics around that price range. Try to look for a solid-top instead of a laminate (if it has a solid top, it'll say 'solid top', it's a sign of quality), but at that low a budget you'll probably end up having to get a split-top laminate. The sound quality isn't as good but it'll do nicely for a starter gitbox.

-Edit- Make sure you check around your local new & used shop. Sometimes you can get a great deal on a used acoustic. Ask if they have any cheap solid-tops.
-Guitar Gear-
1995 American Fender Strat, EMG 85 pup
Randall RH200 Head
Marshall 1960a Cab
Woods Acoustic
-Bass Gear-
Spector Legend 4 bass
Washburn Bantam bass
Hartke HA2500
Fender Bassman 410H
Play what you love, love what you play