My haggling experience was this:
Simple ply door, nothing fancy, used 4 of them in a sliding door carriage. Rang Cribbs (Bristol) where a mate of a mate works, price was £27+vat, Weston Super Mare branch £23+vat but no stock, Bridgwater £17 inc vat and all in stock.
I popped into Howdens Cribbs branch on the way back from a job - where unless they know you, they'll try and do you (speaking from experience) to buy a hinge. The grunt behind the counter suggested it was £5 and wasn't having any of it that days before I had bought the exact same item for £2 at another branch. Out of principle I made him call the Bridgwater branch who confirmed "my price" for them. Bearing in mind Howdens in Bridgwater don't know me from Adam, this "my price" nonsense is just that, they just confirmed what price they sell that hinge for.
Now I have a choice, use Bridgwater Howdens in future, or not take the risk of having to check prices everywhere. Magnet Trade, same thing, no messing about and if you want to try and leverage a bit more money off, they can be cajoled. You won't beat them for construction sheet materials either generally.
Just writing that makes me angry.