Well, here is a site of Dutch Bantams that has a pullet similar to yours. A Geelkoekoek? Certainly a new variety in Holland, maybe not yet approved. http//www.kippencylopedie.nl/index.php?title=Hollandsekriel
Another source of her possible pattern/color...... Sigi van Dort's book...
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...
Mille Fleur (Porselein) Dutch Bantams are an approved variety in The Netherlands, as well as Citroen (Cream) Mille Fleur (Citroen Porselein). They have been imported and are bred and shown in the UK and in the US for over 10 years.
Not easy to breed to a Standard. They were made from...