We are a group of gardeners who don't sell seeds or plants, but we do have a conifer exoert as a member - he'd know, so I'll send him a message to ask him to look at your question, Guest.

If you cant get Pinus longaeva , make do as I have with Pinus aristata . I look forward to news re P.longaeva.

I would be surprised if Pinus longaeva seeds or trees would be commercially available anywhere in the UK. I would suggest you contact Bedgebury National Pinetum, Goudhurst, Kent....If anyone would know, they will....failing that, a trip to the White Mountains in California might be necessary..:0)