It's had a few good upgrades (Thomson seatpost, XT brakes) but it's hard to judge the overall condition, and your pictures omit most of the components. The price guide here looks reasonable - perhaps a bit on the low side:
I'd have thought £200-250, depending on condition of wheels especially. Very large or small sized frames wil go for the lower end of the range as they are harder to find buyers.
The seatpost is back to front, which doesn't create the impression of a caring owner.