I'm not much good with haggling face to face, so tend to do the research and find the "best" deal for me, which often as not is not the cheapest. I won't buy stuff which is notoriously faked from anywhere other than a trusted supplier, things like Makita power tools are a classic case. Buy cheap off the auction sites it's often as not a fake, unless form a trusted trader (usually with a bricks and mortar shop somewhere in the country).
I don't have a convenient Aldi/Lidl, the petrol would offset most of the savings if I drove there. I tend to "play" off Sains vs Tesco, swap between them,