Looks pretty good. But note that the Z87 and Z97 chipsets have LGA 1150 sockets, as opposed to the LGA 1155 socket that Ivy Bridge and Sandy Bridge CPUs require.
I have a 3570k myself, overclocked it to 4.4 Ghz, and it runs everything I throw at it easily. Well, except when I enable PhysX (since I don't an nVidia GPU).
I like all of it. Maybe you would consider the £50 Arc Mini chassis, for a smaller form factor build. Or if you wish to stick with ATX, it's only £10-15 in addition for the Fractal Core 3000.
There's a lot of up-to-date components that are comparably priced, too.
If you're planning on doing any video editing or other tasks that have really good support for 8 threads, I'd pick up an 8350. But if you're just gaming... I think I'd have to recommend the i5. It performs more consistently across a wide variety of games, while the 8350 really struggles on some games (Arma/DayZ, for example).
Tri-X is arguably the best, affordable R9 290. For <£300 you have to activate a prime membership. Just use the free month that they provide, then cancel it later on in the month.
I already have a 780. Paid too much for it when it first came out...! I didn't have a PC, I have an excuse.
Oh, which Z77 board are you getting? Extreme3? 4? 9? I have the Asrock Z77 Extreme3 and I've been very happy with it. Maybe not the best board on the market but it's done everything I've needed it to, and I was able to get it for $100
I always saw the Extreme 4 get recommended, but I couldn't quite fit it in my budget. Still I'd expect it to work out very well unless there's a specific feature you're missing.
According to this thread on tom's hardware: http://www.tomshardware.com/forum/322204-30-asrock-extreme3-extreme4
The difference is that the Extreme 4 has two more USB 3, an E sata port, and a slightly better power phase.
I'm too damn lazy to go through Asrock's specs.
Edit: looking at other sources there appear to be more differences (max memory, audio, etc.). The extreme4 does appear to be all around better.