Have you tried via the RHS 'Plantfinder', which you can find on the RHSite?

rhs.org.uk

This nursery outside Edinburgh has them for £3.00 http://www.kevockgarden.co.uk/store/product/7f11a284-73d6-4e24-aff7-1b26e83d0198.aspx
This nursery sells seeds.
http://www.nickys-nursery.co.uk/garden-shop/seeds/flowers/l/linum.-flavum-compactum

I can vouch for Kevock as we know both of the owners well and they will replace any plant there is a problem with.

Spritzhenry thanks. I did try the RHS plantfinder book, but had no luck in my area.

Scotsgran thanks. Will give that nursery a go if thet do mail order.

Moon-grower, thanks.

Wendy Kevock only do mail order or sell at shows, the nursery is in a very awkward position so they are not allowed to open to the public.