Hiding in the Hawthorn

I found this caterpillar as I was trying to take a shot of the hawthorn blossom. I'm not sure what it is. From a web search the closest I've been able to get is a mullein moth but it doesn't look quite right. Mullein moth caterpillars apparently feed on verbascum (mullein), buddleia and figwort.

Any ideas blippers?

(try as I might, I can't get this image to upload correctly - it should be landscape and not portrait format - the caterpillar should be aligned left to right)