Well to be honest it just felt awkward, and I don't want a pure race position, but something just a little comfier. (plus I may well grow over the next couple of years, and then it'd be way too small.)

Going off what the Decathlon guys said, and what their website chart says, I should get the 57cm. http://www.decathlon.co.uk/size-guide.html (I'm 175cm)

And if it's too big and I have to go back then I'll let you say "Told you so".