Budget PC, first build! i need ze help

i thought id do it by the book this time so.

Approximate Purchase Date: a month or so

Budget Range: 200-350 GBP

System Usage from Most to Least Important: internet, watching movies, basic gaming( total war series, age of empires, civilization5)

Parts Not Required: keyboard, mouse, or screen. i also ave an old ati x1600 or sumthing video card, but i was advised not to put that in incase it fries the other parts

Preferred Website(s) for Parts: www.the-computer-shop.co.uk or anyother well trusted site
Country of Origin: england
Parts Preferences: dual core processor, good amount of ram, not bothered what company as long as theyre reputable

Overclocking: Yes preferably

SLI or Crossfire: probably not  

Monitor Resolution: no clue, does it matter?
Additional Comments: i would prefer it to be upgradable to a decent degree, this my first ever build, never done this before so im gona need some serious help 

i was going to buy a normal desktop from pcworld or something but then i realised they just rip you off. I know my budget isnt great so if we just focus on the core components and leave those that are upgradable to latter that would be good.
ive already looked at some processors (which i always strait with for some reason)

http://thecomputershop.x2tek.co.uk/product/AMD-Phenom-I...
http://thecomputershop.x2tek.co.uk/product/AMD-Athlon-I...
http://thecomputershop.x2tek.co.uk/product/Intel-Core-i...
http://thecomputershop.x2tek.co.uk/product/Intel-Pentiu...

what do you think?
anyways thanks for any help guys

p.s for the things its gona do, this build would be better of using XP right?