It honestly depends on the games you play, your expectations and other usage. The thing about 1440p in my experience was that it was overrated, I didn't think the visual difference was worth the extra burden on the system and the increased cost required to get good performance. I've also come to accept that since I spend most time playing games like CSGO, DotA 2 or Path of Exile, 1440p made even less sense as those games don't scale very well. So, for me, I'm getting a Viewsonic next week and it's replacing a BenQ BL3200PT. I would also say that in some cases downscaling from 4K on a 1080p monitor gave some gorgeous results (e.g. Deus Ex Human Revolutions) but native 1440p compared to 1080p wasn't as big of a difference.
Ultimately, the extra £100 can take you from a 480 to a fury or fury x even, and that's going to do more than just going up to 1440p. On the other hand, if you don't mind keeping closer to 60 fps rather than higher, 1440p isn't too bad.
I do have to say though, I plan on getting a 4K TV for more action-adventure type games and such, so I also take that into account for my choice, but that may not be the case for you. Plus, I'm a bit value obsessed, so knowing I get much more value from a purchase nets me more satisfaction than just getting a better product, i.e. XG2401 for £250 is tremendous, the jump to XF270HU for £110 more is not so big spec-wise and because it taxes the hardware more that means I have even less tweaking room, so that is even less value.
