I'm trying to find somewhere/someone who sells these plants in the UK. Preferably already to a reasonable size. Can anybody help?

Hi, you will not find either of these. Both are highly specific to a single mountain range in the southwest tip of South Africa, and are currently grown in local plantations for making the teas.

The Latin names are Aspalanthus linearus and Cyclopia intermedia.

You could try contacting the growers in South Africa and asking for advice.