Beauties indeed. These are the larvae of the Knotgrass moth, Acronicta rumicis. Common and widespread in the UK but I rarely see the larvae. As far as I know these are not known to be one of the irritant caterpillars so enjoy their company in the garden for the next week or so.
I'm in Bristol and just found one, the kids have named him Spike! I am so glad to find out what he is, like you said, none of the pictures on Google quite matched him...mind, I'm not a fan of moths I may leave it to the hubby to releace Spike! What should I feed him? The kids want to see him become a butterfly (they said he's too nice to be a moth) and seeing as I found him on my hosta I have popped some of that in with him, is that ok?