I became a bit obsessive about this and was willing to spend on lightweight carbon but didn’t because I didn’t like a lot of the geos available.
I think the choice for £2k boils down to frame only alloy spearfish or complete Giant Anthem and change what you can afford for light bits.
I went the Spearfish route and love it. The alloy is only 225g heavier than the carbon but £1,000 cheaper. It’s possible to build to 25.5 real world pounds with Crests, 1x, KCNC etc, Conti protection tyres, normal cassette, comfy saddle etc. Decent wheels, cassette and tyres can get it very close to 24lbs (with shimano pedals)