[Build Help] First time building, just want to check I'm doing it right

I'm looking to make this build cheaper if possible, usage to begin with is primarily going to be gaming, but eventually I'll want to upgrade my system to cope with video and sound editing. I realise the case is cheap, but I want to upgrade that at a later date in order to minimise the initial cost.

I've been building this using the guides on this website using google shopping to try and minimise costs (delivery charges all included in the pricing where necessary)

Intel Core i5 2500K 3.3GHz Socket 1155 6MB Cache Retail Boxed Processor £145.64

G-Skill 4GB (2x2GB) DDR3 2133Mhz RipjawsX Memory Kit CL9 (9-11-9-28-2N) 1.6V £43.00

Asus P8Z68-V PRO Z68 Socket 1155 8 Channel HD Audio ATX Motherboard £144.52

Gigabyte GTX 560 OC Edition 1GB GDDR5 Dual DVI Mini HDMI PCI-E Graphics Card £149.63

Hitachi Deskstar 1TB Hard Drive SATAII 7200rpm 32MB Cache - OEM £89.99

Samsung SH-222AB 22x DVD±RW DL & RAM SATA Optical Drive - OEM Black £13.98

Antec TruePower New 650W Modular PSU £59.99

Coolermaster Elite 360 Black Desktop ATX Case - No PSU £27.50

TOTAL £674.25

(I already have a monitor, mouse, keyboard, speakers etc. that will do for now)

Please be gentle, I'm brand new to this!