Salvia microphylla `Forever Red' is a form I saw in August 2008 at Betsy Clebsch's garden on Skyline drive. She said she got it as a gift from Dr. James Compton. It looks a lot like the S. microphylla grahamii from Far North Gardens that I sent him in the early 80s. Along with S. macrophylla x sagittata Big Swing, it is one of the earliest to bloom well in my greenhouse this spring.
It seems to be mostly available in the United Kingdom and USA (mostly California) through plant sales
Sorry...never heard of 'Forever Red' in the UK. Looks good...BUT we have grahamii, 'Kew Red', var. neurepia...they all look the same!!! Whatever...a truly great plant, but somewhat less hardy than others.