FWIW I buy my pots from Kays Horticultural Products. Their catalogue and web site is a disaster - so little information it is hard to make any sort of purchasing decision, unless you know exactly what you want - e.g. searching for 1/2" hose is hopeless, lots of matches, impossible to work out what you might want.

Anyway, their pots are good quality Sankey, and the 9cm ones (for comparison) are £ 4.75 - but ideally you need to buy in multiples of a case (which for 9cm is 1,320) at which point the price drops to £ 3.48 / 100.

Fixed delivery charge of £ 5.95 - so only really worthwhile if you bulk up the order.