In reply to Tall Clare: I have a roundback Applause electro-acoustic guitar (Ovation's cheaper brand, like Squier is to Fender for example), and it is absolutely fantastic, £140 from eBay brand new. I put 9 gauge electric strings on it and it plays very similarly to most of my electric guitars, and is much more friendly on your fingers.
I've been a guitar geek/player for twenty years or more, and I own Fender, Kimbara, Musicman, and Zion instruments to name but a few. I would say with the electric strings on it the Applause plays most like my Ibanez Jem, which I love.
I've had a dreadnought acoustic in the past (similar to a Martin), and it was too big for me, I found it uncomfortable to play and so I got rid of it. Some of the slimline acoustics are good too, and handle more like an elactric guitar in terms of fitting the contour of the human body.
Like others have said, guitar choice is a very personal thing - I, for example detest the feel and playability of a Les Paul, much to the lambasting of several of my guitar playing friends - they are hugely popular and well-made instruments, just not my cup of tea. I much prefer the Strat type shape myself, it's far more comfortable for me.
Don't listen to the "avoid such and such like the plague" nonsense, many cheap guitars, if set up properly, play pretty well. A decent music shop will be able to help you here, there used to be (and possibly still is) a really good guitar shop on the right hand side of the inner ring road coming in to Leeds from York. I can't remember the name - Music Ground or something?