By shopping around you should be able to build up an XT based ASR5 for around £3500.
I did mine for not much more with XTR back in November using some of the “spend 100 pounds and get a 50 pound voucher” from CRC at the time which helped.
The cheapest way to buy a groupset is via the German sites especially with the strong pound at the moment.
So with some haggling:
ASR5 Frame and Fox 32 140mm forks = £2k
Group set (XT including brakes) = £490
Disks = £60
Wheels = £400
Easton Haven Bar = £70
Easton Haven Stem = £70
Tyres = £60
Grips = £20
Reverb Seatpost = £180
Cost = £3350
so room for more goodies like headset, saddle etc.
Go for it, its a great bike!