Just found your blog. Yesterday I had the thrill of seeing a Purple Emperor here in Kent (Otford, on the North Downs) - feeding on buddleia. I know they're not supposed to do that, but it was (and I filmed it). :)
I've attached a couple of the pictures I took with my phone. It fed for about 5 minutes, then flew off.
I'd seen it about 20 minutes earlier flying around a bramble/old man's beard hedge and knew it was something I hadn't seen before, but couldn't see it clearly then.
There is a goat willow in the garden, and I think there are a lot of goat willows in a wooded area nearby.
From Di Napier