In reply to Run_Ross_Run: You can do it way, way cheaper than £3k (indeed you can buy a bike from Rose or Canyon with a top spec for less than that) by bying a frame and the bits then finding a mechanic to screw it together or doing it yourself.
Westbrook Cycles were doing a Scott Foil Team Issue frame (top quality carbon frame, forks, headset, seatpost) INCLUDING 11sp Ultegra Di2 gearset (shifters, derailleurs, battery and cables) for £1400 a couple of months ago. Buy a chainset (£140), brakes (£50?), chain (£25), cassette (£35). Either reuse saddle/bars/stem or buy decent ones for <£200 all in. RS81 wheels about £350. Cables about £20. Tubes and tyres another £50. Result: <7kg bike for about £2100.
I swapped my groupset/wheels/finishing kit from my old "best bike" across onto the same frame and sold the Di2 bits for £400 - the same bike in 2013 (it's a 2013 frame) would have cost about £8k.
But have a look at Rose - mate's just bought a carbon bike with Ultegra Di2 and top quality finishing kit for about £2200.
But if you decide to go upgrade, Bike24 (German, but great service) have the new 105 11sp groupset for EUR420 - about £360?