Used Plumbworld for some of the purchases for a bathroom refurb. Prices on most things were cheapest (although they do vary day by day, so if you spot a good deal you need to be quick). Delivery by their freight company was good - drivers were friendly and helpful. Good information on out of stock items and likely availability.
Bought the wrong shower tray (my fault), but the returns process seems to be fairly good, so keeping fingers crossed.