Sorry, I had not noticed Scotland.. Of course, your Lavenders will be pure Dutch. We just do not have them in the US, but do have crossbred with American OEGB in what is named Self Blue.
"Porselein", is the Dutch name for the variety we call Mille Fleur. So you need Mille Fleurs X Lavender. While Porcelein is the name we call the lovely soft color in UK and US, it is bred in the Belgian Bantam breeds. Do not use a cross with a Belgian.
Not "lemon", but Citroen Mille Fleur is the variety needed to ;produce a Porcelein bred variety (not any where I have seen to date).
I raise both Mille Fleur and Citroen Mille Fleur with birds from Holland--and like them VERY MUCH. I added Blue to make Blue Mille Fleur, but they are not distinctive, and discontinued them. They are not bred in Holland. Breeder in UK sent pictures of hers, not at all attractive. She quite them, also.
Will be back with a website address for you, that will also picture the dear bird your breeder has produced.