Welcome to BYC! Despite what many "chicken experts" say, there is a such thing as a large Silkie. However, I read they are common in Australia, like bantam Silkies are in the U.S. (and probably the U.K. too). I'm not sure where you could get any though. Have a great day!
I'm an Aussie and can say we do not have giant silkies (as far as I know), and agree with drumstick diva that their size is a large part of their charm. (sorry if I ruined your hopes and dreams)

I was actually just talking to my husband last night about it, and then I stumbled onto your post! And I'm hoping to start a large silkie breeding project hopefully this year if not next. We just moved out on 40 acres and as soon as I can get some coops set up I'm planning on breeding the largest silkies I can get my hands on! For pets, meat, and extra large broody hens. Regular sized silkies are hawk and eagle bait here so I want something that's harder to carry off if you catch my drift lol!
welcome to BYC !!