Do you need an OS or do you already have it?
Done a spec below, but what is the max size case you want?
YOUR BASKET
1 x Intel Pentium G620 2.60GHz (Sandybridge) Socket LGA1155 Processor - Retail £47.99
1 x Gigabyte H61MA-D2V Intel H61 (Socket 1155) DDR3 Motherboard £39.98
1 x Seagate Barracuda 7200.12 500GB SATA 6Gb/s 16MB Cache - OEM (ST500DM002) £39.98
1 x OCZ CoreXtreme 500w '80 Plus' Power Supply £27.98
1 x BitFenix Merc Alpha Gaming Case - Black £26.99
1 x Kingston HyperX Genesis Grey 8GB (2x4GB) DDR3 PC3-12800C9 1600MHz Dual Channel Kit (KHX1600C9D3X2K2/8GX) £25.99
1 x OcUK 22x DVD±RW SATA ReWriter (Black) - OEM £13.99
Total : £237.01 (includes shipping : £11.75).
Does`nt need a hdd, mate.