www.savastore.com
www.overclockers.co.uk
www.eclipsecomputers.com
They are some good sites, got my computer case from savastore (went to the actual shop as it's not too far from me and i wanted to see the case up close first)
www.overclockers.co.uk is an awesome online shop...but look around for cheaper deals maybe...post on here with any other sites you find so we can see if they're known/trusted
Matt