Frank,
I don't know if your using the term
mottled to cover what is said on page 111 of BGBtW, or whether your information is from another page. Just in case, I draw your attention to the entry on that page.
I do know that in Charles H's long awaited sequal book, on 20th Century British Glass, he will have an entry on Haden, Mullet & Haden. Although he showed me some illustrations he was proposing to use, sadly, I'm not privy to what he has written

I bought a part of Jack Haden's archive a couple of months ago, but I haven't come across any information about the company in the books and pamphlets I'm afraid - many of which I've never come across before. I'll keep looking as he had lots of obscure material and it would be good to find any detail that could be helpful.
Nigel