Thought you might all like to have a look at this yellow lavender + have a peek at their plant list. I know it's another American one but just thought it might give you some ideas. ;) ;)
http://www.mountainvalleygrowers.com/lavviridis.htm
Eileen.
How can lavender be yellow hahaha? pretty expensive too I see. Looks interesting.
In real life it is more green than yellow and on the tender side. We used to manage to grow it, but even in our old frost free (ish) garden it had to be kept in the greenhouse over winter.