I need help choosing a £400 - £500 Gaming desktop or a £450 - £530 Gaming laptop?

[I need halp]

Hey, guys. I'm new to this forum. Anyway, I've been looking for a gaming pc for a while now, and my searches have been.. Unsuccessful. All the pcs are very out dated and all the websites where you pick your own parts don't really have any way to contact them. I've literally been banging my head against a wall it's that annoying. The games I'd want to run are:
ARMA 3
DayZ
BF4 (possibly)
7 days to die
Chivalry
Skyrim
And more, obviously. I have around £500 budget, but for a desktop I need a monitor, keyboard etc so I put some money a side. I could get a more expensive laptop because I wouldn't need all that stuff. Can anyone help? I'll be very grateful.

Thanks

 

[stickmansam]

Here is a basic build and should leave you enough for OS, kb+m and screen

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: AMD Athlon II X4 760K 3.8GHz Quad-Core Processor (£60.91 @ Scan.co.uk)
Motherboard: MSI FM2-A75MA-E35 Micro ATX FM2 Motherboard (£44.10 @ Scan.co.uk)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory (£70.98 @ Amazon UK)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive (£46.78 @ Scan.co.uk)
Video Card: PowerColor Radeon HD 7850 2GB Video Card (£139.32 @ Amazon UK)
Case: NZXT Source 210 Elite (Black) ATX Mid Tower Case (£38.65 @ Scan.co.uk)
Power Supply: EVGA 500W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply (£41.40 @ Scan.co.uk)
Total: £442.14
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-11-05 00:16 GMT+0000)