don't know what this is

I think it's part of a Hydrangea.

I'm sure it's the skeleton of a hydrangea flower, I've got some like that on mine.

...I was going to say hellebore, which it probably isn't...:>)

It is the bract from a Hydrangea flower. Hydrangea flowers are the bits in the centre. Here is the definition of a Bract from the on line dictionary.
BRACT A modified leaf growing just below a flower or flower stalk. Bracts are generally small and inconspicuous, but some are showy and petal like, as the brightly colored bracts of bougainvillaea or the white or pink bracts of flowering dogwoods. In this case Hydrangeas.
They are brightly coloured to attract pollinators. They make inconspicuous flowers very noticeable.

Thanks for the definitive answer Scotsgran! I didn't know about the bracts on Hydrangeas, but I do now!:)

Thanks Louisa, I did a blog on Hydrangeas on 12th September 2012. Its on Page 2 of my blogs if you want to have a close up view of the actual flowers.

Just been to have a look at it, thanks, I can see I've got a lot of catching up to do on GoY reading lots of superb blogs I missed before I joined up!:)