what dimensions do you want?
On Ones have a long top tube which suits those with long torsos and arms. I find ‘regular’ frames a bit cramped in the top tube as I have to go for a size based on stand over.
£1k is a nice budget for a frame so you need to go try a few for fit as that is the most important – tweaks can be made with post, stem, bars etc but the wrong frame is the wrong frame.
I would deffo take a look at the carbon 456 or Ti 456 (heavier but more compliant and carefree) If you don’t want an over 4″ travel fork then maybe the carbon whippet.
Also take a look at the Lynksey Ti frames and the Ragley – you have mentioned piglet but I am not sure what is coming out in the ‘X’ range (better steel so can be built lighter) and they have Ti ones coming out iirc.
The Cotic and Cove are nice but seem a bit shorter.
You could also look at 29ers – again On One have some coming out – Ti and carbon but lots of other makes too and could be a better buy. Don’t forget to budget in a decent fork as it would be a shame to stick an unresponsive heavy one up front.