Keep it, use it for winter.
26 inch bikes ride great and i say that as someone with a 27.5 too, i found bigger wheels on a HT made it boring but bigger wheels on my FS made it more capable and had me wanting to hit stuff harder/faster…couldnt get rid of the 650b hardtail fast enough though!
As a complete build you’ll have to come way below 1k i think, sad really as its a good bike but the mindset that pervades MTBing at the moment is that 120mm of suspension isnt enough which is ludicrous when you see the awful standard of riding being displayed out and about on the trails!….nothing like a bit of self delusion and the industry helps matters by pushing the idea that you need 27.5 inch wheels and at least 140mm to ride around a trail centre.
I reckon somebody will buy it for £750, you may get more if you split it but its hassle and might take ages.
Like i said at the start of my post, i’d ‘winterise’ it…fit narrow mud specific tyres, cover it in WD40/GT85/ACF50 etc (not the brakes obviously) and use it when the weather is grimmest, hose it off in the spring and put it away until next winter….makes use of what is still a good bike and saves your new one from the worst of the conditions.