I use the garland 2ft square trays as the fit perfectly in the greenhouse, no wasted space !
Anyone local to this place can pick up supplies in bulk, cuts the cost down on pots & labels bhgsltd. They will deliver too but havent a clue how good or bad that service is.
Again, I buy the slightly more expensive, TEKU pots, but they should last a long time so to me makes more sense.