You can pick up the Giant Defy composite, full 11 speed Ultegra groupset (roadie equivalent of XT) for £1200. It's got own brand Giant wheels on it (road bikes usually save money on the wheels, you will normally buy £2.5k - £3k bikes with entry level wheels that retail at not much more than £100 the pair), but apparently they're badged DT Swiss and are actually ok.
That said at that kind of price point there are always massive compromises. Usually it is the wheels, but also poor quality finishing kit is pretty much the norm.
If you're looking for a bike that's good for training etc, as well as for the actual race, you might want to have a look at Kinesis. A couple of mates of mine who are very serious roadies have them as their winter bikes. They reckon the frames are pretty much as good as you'll get (unless you want to spend £1,500+ on the frame alone) and struggle to notice any clear performance differences between the Kinesis and their £4k+ carbon dream bikes.
I'm building up a bike of theirs for myself. For £1,500 you can get a top tried and tested frame/fork combo, with wheels that you would get on a £4k off the shelf bike and top of the range finishing kit. I'm building to a £1k budget but yours to £1,500 is as follows (everything priced from Merlin cycles other than frame and forks from Kinesis):
Kinesis T2 frame - £240
Kinesis DC07 Carbon fork - £140
Ultegra 6700 Groupset (10spd), incl cables - £540
Fulcrum Quattro wheelset (aero wheels, very light) - £240
Stem - FSA OS 150 - £35.00
Seatpost - Richey Carbon - £50.00
Collar - Hope - £15.00
Headset - Richey WCS Logic - £40.00
Bars - Easton EC70 carbon - £80.00
Bartape - Lizard Skin - £25.00
Saddle - SDG Falcon - £30.00
Full cost of build - £1,400 or so + £100 for a good mechanic to put it all together for you. All components from same shop so no messing about.
My build is with Tiagra and RS31 wheels but I'm starting to wonder whether I should upgrade to that spec
Good luck whatever you choose, but you get way better value at that price point buying a good frame and forks and building it up and Kinesis work so well because their T2 frame is ridculously cheap for how good it actually is..