If the case itself came with a PSU,
I'd be biting your hand off for that one, as it would be an Antec PSU (which are far from the best, but a million miles from the worst too - fine for this sort of budget build). Sadly the case doesn't include a PSU, which means it's something picked up off of the shelf at Novatech... unfortunately, once you've priced up all the components from Novatech (choosing the cheapest of each), you're left with £20 for the PSU... and guess what comes in at just under £20... elcheapo
550W Novatech-branded PSU.... so a rebranded Q-Tec or EZcool or similarly dangerous micro-explosive (no exaggeration - just ask Dave... a Q-tec set his wallpaper on fire...).
Judging by the spec page and Novatech's own support, that PSU doesn't even come with the 6 or 8-pin power connector needed for the mid-high range graphics cards (say £80+). They've been around for 5 years now, indicating just how old these Novatech PSUs are. How many cables it does have (motherboard + 1*sata + 4*molex + 1*floppy) shows just how under-performing it is.
By all means buy the barebones system above, but do it on the proviso that you'll want to change the PSU before it is even switched on. If you do intend to run it with the included PSU, then do so at your own risk (our reputations aren't going to be tarnished when it takes out the rest of your system), and under no circumstances whatsoever should you run it with a dedicated graphics card installed, because it just won't cope and will damage other components.
Of course, for that barebones you will need to buy a hard drive and DVD drive to go with it, but they're easy to install. You'll also need an operating system license. With a 500gb hard drive, a standard DVD drive and Windows 7 you're looking at £150 on top of that £270, unless you're a student, in which case you can get Windows 7 for £30, bringing the total cost down to around £360... before PSU & graphics card. What looks like a bargain quickly starts to get expensive.