In reply to Ian.Hogg:
Two possible, but not ideal...
Canondale Quick Disc 1 is slightly over weight at 10.5kg at £1000
Decathlon triban 520 flat bar is also just over at about 11kg. At £730
Both flat bar. A bit heavier than you wanted but 105is good kit. Possibly not low enough geared if you want a really low ratio for hill climbing.
Slight ly closer to what you want :
Giant fast road advanced at about 1700 touches under 10kg. Fast road sl at about 1000 and just over the 10kg. Again gearing could be a problem.
I'm surprised how heavy bikes are still at the £1000 mark when they are flat bar. Drop bars seem lighter. E. G the giant contend sl disk is under 10 kg for £1300, £400 cheaper than the fast road.
The word Gravel seems to add about £300to the price for manymanufacturers.
Or push thr boat out and get a ribble e bike https://www.ribblecycles.co.uk/ribble-cgr-al-e-grey-105/ heavier than your wanted but power up the hills!
Good luck.
Post edited at 21:34