I went to a garden last week to do a bit of maintenance and they have this plant - it is just about beginning to come into leaf, and we're in London and the plant is in a very, very sheltered spot. Yours may take a little longer to show signs of life, but should be showing something within the next fortnight at most.

They do look horribly dead while they sleep! Try scratching a little bark off one of the mid-size stems--slightly thicker than a pencil--and see if the inner bark isn't moist and green. If not, try again with a larger branch. Fortunately, even if the top is completely frozen, it will regrow from the roots, but it would be racing fall frost to produce blooms this year.