I phoned containerwise and they sent me a smaller number of trays, for a fairly high delivery charge (as I would expect, because they aren't really setup for smaller orders). It was worth it because I ordered a lot of trays. So it might be worth giving them a call.
I also bought some from our local allotment shop, as they trialled buying in a pallet-load. If you have an allotment shop on your site you could request they try this.
I really like them - they are robust and so easy to use, much less fussing. Well worth the money. The smaller trays have larger holes at the bottom, so you can push the plugs out easily. Compared to similiar-priced products, they look much better to me.
Your link is to the larger trays, I think. you get a lot more plugs per £, but they don't fit on a windowsill as the smaller ones do, and in practice I have only really used these for autumn to very early spring sowings, because I am not down the allotment every day to water the greenhouse.
Hope that is of some help!