You would need to put in the plant name and cultivar for the ones you want, so for instance, Lamium 'White Nancy' or Agastache or whatever.

pdb , ive just googled the above and come up with www.chilternseeds.co.uk and www.raybrowns.co.uk
They both do seeds for what you want , i hope they can help you out

I'm not sure I agree with Carol Klein about the red dead nettles she was referring to. Arguably, they are very pretty, but can be a very invasive weed. They self seed very readily.

Thanks Bertiefox. It was the Lamium orvala she was showing. Yes I am now having second thoughts about it as a few people have said they are very invasive