You build sounds good.
Here's the build I'd recommend, or something similar:
Intel Core i5-4690K, Asus GeForce GTX 750 Ti, NZXT S340 (Black) - System Build - PCPartPicker United Kingdom
Use
uk.pcpartpicker.com to build it and to scope out the prices, also check
www.hotukdeals.com for any good sales on any of your parts.
CPU: £170 for the i5 4690k, it will be sufficient for all you gaming needs and everyday tasks. Downgrade to the i5 4460 if you do not plan to overclock anytime in the future. This will save you around ~£35 by doing so.
Cooler: Stock cooler will do, if you plan to overclock choose the H80i GT
£80 / H100I GTX
£90 for water-cooling, for a high end quiet air cooler choose the Noctua DH-D15
£70, or everyone favourite budget cooler the Hyper 212 EVO
£25.
Motherboard: Any Z97 motherboard will do. If you're not overclocking choose any H81 or H97 board, whichever is cheapest and suit your needs the most.
£50-£70
Memory: Any (2x8GB) 16GB DDR3 for around
£60. Save ~£20 if you choose only 8GB.
Storage: Definitely buy an SSD. Wait for around Black Friday as 240GB SSDs usually go for sub
£50, and 480GB ~£90. Pair it off with a 1TB hard drive for
£40, if you want to save on this just use your old one, that is if it uses a SATA connection.
GPU: Any 750ti you want
£90. Might be cheaper by about £10-£15 around Black Friday.
PSU: Do not skimp on this. Choose a gold efficiency one. You want about 650W to give yourself some breathing room if you plan to upgrade to a high end GPU down the line. If you don't plan on upgrading 550W would be fine. Scan have a great deal on the Cooler Master VS 550W Gold PSU right now which costs about
£44, definitely won't be able to get any better even on Black Friday. The Cooler Master VS650W is priced respectively at
£54.
Case: Choose any you want depending on size. Obviously, choose the other parts compatibly if choosing MATX or ITX rather than ATX. Prices usually the same for an MATX build, a bit more expensive if ITX.
£50-£80
OS: I'm sure you'll be able to find a decent deal for this somewhere. If you know any university student you can ask them to get a copy of Windows 10 for free.
£0
If you buy all according to that should end up with a build that is
£500-£650.
For a Skylake equivalent build i5 6600k
£200 or i5 6600
£160, Z170 motherboard
£80, DDR4 16GB
£70. Though all probably going to be cheaper on Black Friday. All in all, probably around ~£50 more than Broadwell, if you decide to go down that route.