Middle ground for carbon HT does seem a bit barren. Low end you have likes of On One, then there’s loads of nice high end offerings, but a big gulf in between. Seems that the best bet in this area is to buy a full build from the likes of Spesh, Trek, Scott, etc. and sell the bits you don’t need. Though rather obviously if you want to be faster uphill there are better things you could do with your cash.
Edit… I know you said carbon but if you want something for XC blasts you might want to consider something like an alu SC Highball. Especially at bargain 360 quid if you’re a S or a M.