Best would be to pay Robbo. I can post the stickers off to him, and he can simply add the stickers to the shirts without any extra shipping costs.
By the way, I have fiddled around with the sizes. Martini gave me a size of 28½ cms wide, but I think that's way to big for a small car. So I have printed 28½, 19 and 12 centimetres wide.