So I’ve just had a quick play with the sicklines weights sheet building a Chinese hard tail with Chinese knockoff parts where possible from aliexpress only (some stuff just Chinese brands that aren’t obvious knockoffs) and got to about £950 including everything you will need (cables etc.) and about 9.3kg if you believe claimed weights! 1*11 gears, carbon wheels, seatpost, saddle and bars(integrated stem for fun)!
I bet you’d be stung on import for a few bits but likely only frame/wheels/groupset/forks and maybe bars which will ad a £100-£300 but still surprisingly cheap!
Would be interesting to see how this compares the the fully British bike being talked about a few weeks ago! I reckon you can knock another 0.5-1kg off this by buying more premium parts as I’ve just gone for the top ordered or near that!