the surface 3 pro i3 64gb/4gb model which is around £520-530 at the moment. Now you're going to say it's £100 more but it isn't when you add in the stylus for around £40... making it £60 more to get a better slate in all but 1 hour of battery life and arguably being a little bit bigger (some might prefer that aspect too).
To me grabbing the i3 model is a better deal, better cpu, better gpu, more ram, likely faster ssd, screen could be argued is better (it's basically same pixel density though) and a multi position stand.
If the surface was core M at £429 then yeah I would say ok value but it's not it's an atom, the cheapest cpu/gpu from intel and also the lowest performing.
So you have an option then..terrible huh? Either way MS sells you a Surface.