10x20 seed trays in the UK

[Dave Rennie]

I see a lot of American youtubers using 1020 seed trays, which I guess stands for 10x20 inch.
They give formula such as seed densities etc for these seed tray size, but I can't find these in the U.K.

Does anyone know where you source these please?

Thanks

[Thelma Sanders]

British seed trays are near enough three quarters of the size of American trays - so use 3/4 in number (or weight) of seed at the same density/spacing.

[Dave Rennie]

British seed trays are near enough three quarters of the size of American trays - so use 3/4 in number (or weight) of seed at the same density/spacing.

Thank you Thelma,
If I can't manage to find them, I'll use 3/4 measurements for everything.