Maybe about £90 or so depending on what brand motherboard u go for u can get a pre installed one like from novatech pretty cheap the ram/cpu is already installed like. Also depends if uw ant amd or intell m8ty :Cheers:
http://www.overclockers.co.uk/ has some good offers ive been using them for years now all their products are covered and they dont mess about if you need to return something.