Sigma (Martin) here. Martin guitars tend to have a lighter action to Gibson and Epiphone. Once I would have suggested Seagull guitars, a Canadian make. A friend’s daughter bought one for £100, with a one-piece top, years ago, but you won’t find one for that price now. There are some good £100-150 starter guitars around, it’s worth doing a google, and find some guitar fora for user recommendations. A guitar is a very personal thing, subtle differences in neck width, camber, fret height, string height/action, can all make an otherwise lovely instrument almost unplayable for a beginner, although a lighter set of strings will make a big difference to a heavy action, if its hard work to fret near the nut, causing fret buzz, and difficulty doing barr chords then it’ll be no fun learning.
Edit] there’s some nice guitars reviewed here: http://www.musicradar.com/tuition/guitars/10-best-acoustic-guitars-under-300-217607/1
All under £300, you can’t go wrong with a Yamaha or a Taylor, Yamaha’s have been the mainstay of the folk circuit for donks, and Taylor guitars are played by some of the world’s best singer/songwriters.
http://www.dolphinmusic.co.uk/category/guitars/acoustic-guitars
Edit] http://www.dolphinmusic.co.uk/product/7961-yamaha-f310-acoustic-guitar-natural.html
I really don’t think you’ll beat this little beauty, a Yamaha for under ton!