In reply to Carpe Diem:
Some hand built wheels with a good alloy rim can be customised to meet your specific needs (weight, riding style etc) and will be as light and strong as a factory built set. The other benefit is that if you break a rim somehow, it is generally far cheaper to get them re-built than fixing some factory wheels. At that price you will be scraping the barrel to find a carbon rim, and you certainly won't get a wait saving worth sacrificing the quality of the rest of the components for.
For about £500-600 you could get H Plus Son Archetype rims and with either Royce or White Industries hubs with some light spokes - that would be an awesome pair of wheels. A good wheel builder will advise on the detail (number of spokes, lacing pattern etc). I recently got a new wheel from dcrwheels, service and quality was great.