Top building tips:
Read everything, especially reading the case and motherboard instructions are vital.
You need a big clean table
You need to recruit a local PC guru to help with your first build
An extension lead for power
Monitor
Wired kboards and mice can be a big help
A desk lamp so you can see
Containers for small bits
Collection of clean tools - little screwdrivers etc
Get set up well it will take sometime
Okay I say buy the best case and PSU you can afford, and keep them for 10+ years, these are keepers and the PSU has a 5 year warranty.
You have the other parts to recycle.
Using i3 and this gfx card is a great sweet spot. The GFX card has a bios switch, have a read about it.
In the future you can ebay the i3 and drop in an i5 & cpu cooler as an easy upgrade. Or add more ram (up to to 8gb).
YOUR BASKET
1 x
Sapphire ATI Radeon HD 6950 "Dual Fan Edition" 2048MB GDDR5 PCI-Express Graphics Card £215.99
1 x
Intel Core i3-2120 3.30GHz (Sandybridge) Socket LGA1155 Processor - Retail £101.99
1 x
Gigabyte Z68AP-D3 Intel Z68 (Socket 1155) DDR3 Motherboard £84.98
1 x
Fractal Design Define R3 Midi Tower Case - Black Pearl £84.98
1 x
XFX Pro 550W Core Edition '80 Plus Bronze' Power Supply £59.99
1 x
Kingston HyperX Blu 4GB (2x2GB) DDR3 PC3-12800C9 1600MHz Dual Channel Kit (KHX1600C9AD3B1K2/4G) £17.99
Total : £580.92 (includes shipping : £12.50).