For anyone wondering, I went to a camera shop and compared the Lowepro pro runner x450 aw ii (what a mouthfull!) vs the Thinktank airport takeoff II believe it was called).
Weight:
LP slightly lighter than TT. Those panicking about it weighting 3-4kg without any content, let me assure you that any able person will be able to pick this up with ease. It does not feel like it weighs much.
Features:
LP has very similar features to TT. In fact I think LP's inside structure for laptops etc. is slightly better. However, the strap mechanism on the TT are better, as the LP must be hooked on to at the bottom, and this is a bit fiddly if you're not used to it.
Price:
LP new is around £240, TT new is £360+ I believe.
Summary:
I ended up getting the LP as the extra £100+ doesn't warrant the better strap mechanism, but also the added weight. LP also has a good inner system for laptops/tablets etc.
It'll be good for rolling wherever possible, but to backpack it when required, e.g. dirt tracks/gravel and stairs.
Hope this helps anyone in the same conundrum.