I'm posting on behalf of a friend. He's looking to build a new gaming PC and has these parts in mind:

CPU Intel i5 2500K - £163 @ Novatech
Mobo + CPU cooling Gigabyte Z77 D3H with free Arctic Freezer 7 Pro - £80 limited time offer @ Ebuyer
RAM Corsair 8GB XMS3 1600MHz - £35 @ Ebuyer
HDD Seagate 1TB Barracuda 7200RPM 64MB cache SATAIII - £66 @ Ebuyer
SDD Crucial M4 120GB - £90 @ Ebuyer
GPU Sapphire Radeon HD 7870 2GB - £250 @ Ebuyer
Case Corsair 600T White Graphite ATX Mid Tower - £130 @ Dabs
PSU PC Power & Cooling Silencer MKIII 600W Modular PSU - £67 @ Ebuyer
Mouse Logitech G400 - £26 @ Amazon
Keyboard Microsoft Sidewinder X4 - £32 @ Amazon
Wifi TP-Link TL-WN781ND 150Mbps Wireless PCI Express Adapter - £9 @ Amazon
Monitor LG IPS235V IPS LCD LED 23" - £135 @ Ebuyer

How does it look?

I think it's a good build.

The only mild concerns I'd have would be with the CPU cooler and the power supply.

The cooler isn't a problem, but I'd imagine that your friend would probably want to overclock the i5 2500k, and the cooler might start to limit the OC as the voltage/temperature increases.

It's free, so no harm, and if it does become an issue then (at some point where they have some more money to spend on PC equipment) they can simply throw in something, say, from Corsair's Hydro series, which are pretty good for the price & are much less of a hassle to install*

The PSU isn't really a problem either, but it would become a bottleneck if your friend would like to throw in an extra GPU (700W+ would be needed for that), or even with just an eye to future proofing - I tend to cannibalise my older rigs for parts when I'm upgrading, and until recently I had the same PSU that I bought 4 years/2 builds ago, & oddly enough, I only changed because it didn't fit properly in a 600T - I checked the dimensions of the PSU listed here, and it'll fit just fine, my PSU was fractionally too tall).

The build is already slightly North of £1000, and if Crossfire etc. isn't an immediate concern then I'd say your friend is good to go.

*the case is similar to mine, and it was the easiest build I've ever undertaken - really well designed.

Thanks

He asks if the 600T case can hold a 2.5" SDD easily, or if he should get some brackets to fit it into a 3.5" slot?

I haven't actually switched to an SSD boot drive yet, so I can't speak to how well this works, but Corsair certainly say 2.5" is supported:

Six drive bays with 2.5in SSD support
The six drive bays accommodate both 3.5” and 2.5” hard drives and SSDs with no adapters needed.
Snap-in mounting brackets facilitate installation and configuration of 3.5” drives, while 2.5” drives can be
installed with the included screws.
Source