I think that if you are going to buy for £1000, even if you are a beginner, it is definitely worth buying second hand. Ebay usually has a good selection, but you can also find good deals in the classified section of most cycling magazines.
Second hand for £1k you should be looking at full carbon with 105/ultegra (or campag equivalent) vs alloy/carbon tiagra/shimano base range for new. No brainer really.
One tip though, its definitely worth getting measured so that you buy the right size. Either go to a reputable bike shop or use and online tool – this one is good: http://www.competitivecyclist.com/za/CCY?PAGE=FIT_CALCULATOR_INTRO