Beyond that i'd look at the 4GB Nitro 480 - it's just a better price point than the 8GB and pretty much all of the 1060s.
I couldn't have said it better myself and besides:
I am planning on getting a 4k monitor but not anytime soon. I don't really want to buy a card for the future, I'll replace if required.
A cheaper card works out better as a temporary replacement. At 1080p, more than 4GB VRAM is unnecessary and more than 970 performance is also unnecessary. At that, you could even look at getting a 970 or a 390 for closer to £200 too. Just that they won't be as power efficient, but that's up to you and what your PSU is rated at.
If you want AMD, drop down to below £200 and grab an RX480. The best price to performance below £300. If you want Nvidia, still spend around £200 on a decent 970. Even a 980 at under £300 is tough to recommend since it is a temporary upgrade and OP plays at 1080p. I was also personally recommended a cheaper 970 over the 980, a year back by most folks here on these forums (970 at under £300 and 980 under £400).
Cards like the Fury/980ti, etc are overkill for 1080p, in my honest opinion. I'm very tempted to upgrade to a 980ti myself, but I'm still on a 1080p monitor and have decided not to for now, simply because I won't see much improvement still playing at 1080p. The extra FPS won't be visible on my 60Hz monitor. Fury, Fury X and 980ti are cards more suited to higher resolutions, like 1440p. Especially the HBM cards, they don't perform as well at 1080p.
Save that extra cash for a monitor and bigger GPU upgrade in the future.