A 980 is doable for £1500 I think your going to want more GPU power on a 1440P screen. Some of this is on this week only.
Going cheaper on the PSU (your one is overkill), switch to an air cooler and use a cheaper motherboard taking advantage of a bundle saving. For £5 more you can switch to the Gigabyte Gaming 5, Asus about £15 more.
EVGA GeForce GTX 980 ACX 2.0 4096MB GDDR5 PCI-Express Graphics Card £449.99
MSI Z97M Gaming - Devil's Canyon i7 4790K CPU & Micro ATX Motherboard Bundle **£12 Saving** £397.98
BenQ GW2765HT 27" Widescreen LED Gaming Flicker FREE Monitor - Black £299.99
TeamGroup Vulcan RED 16GB (2x8GB) DDR3 PC3-19200C11 2400MHz Dual Channel Kit (TLRED316G2400HC11CDC01) £89.99
SuperFlower Leadex GOLD 650W Fully Modular "80 Plus Gold" Power Supply - Black £87.95
Corsair Carbide Series Air 240 High Airflow PC Case - Black £75.95
Raijintek Themis Direct Contact CPU Cooler £19.99
Sub Total : £1,184.86
Shipping : £13.75 Ex.VAT
VAT : £239.72
Total : £1,438.33