Hello and welcome. I'm sure you'll enjoy cycling on a road bike - it's a whole new experience.
Wrt to recommendations for a new bike, I'll have a rifle thro some back-issues of Cycling Weekly who frequently do reviews of bikes in different price brackets. I'll post you back tomorrow!
I presume you haven't got the opportunity to acquire a new bike thro a cycle-to-work scheme?
Out side you range but worth looking at is the Boardman road bike for £699 on the
Halfords web-site. Good frame (carbob-alu mix) and good groupset (Shimano 105).
Other favourite web-sites to get a feel for what you can get for your money are wiggle.co.uk,
ribble.co.uk, planet X, chainreactions. Look at for previous years (ie: 2008 or 2009) models - sometimes you can pick up a bargain.
Get back to you tomorrow with any results from reviewing the mags.
Welcome aboard!