For good quality acoustics at around the £300 mark, you've got a hell of lot of choice. One thing I was told when I was searching for an acoustic was to go for something with a solid soundboard if at all possible - it can make a big difference to the overall tonal quality of the guitar - try one with and one without and hopefully you'll notice the difference - I certainly did.
Yamaha would be a very good place to start though - there's something in the range for more or less all tastes - electro, non-electro, small bodies, dreadnoughts. I've had my APX4A electro for getting on for 10 years, and a friend recently bought the updated version - the quality control doesn't seem to have slipped an inch. They're all very well built and sound excellent for the money, as well as having a good setup straight from the factory. They're pretty hardwearing too.
I can honestly say I haven't had a single problem with mine. I've played it pretty extensively too - it's done a lot of open mic nights and acoustic gigs over the years, and been lent to some fairly heavy-handed players without incident!