If it has turned to wood, the you will need to dig it up and replace it.

when pruning they always say to prune just above the woody parts, as the woody parts do not produce new growth.

It sounds to me like your plant passed its prime.
:-(

It is such a shame for a plant which looks nice and smells lovely.

im sure you can cut it back to get what you want but i am unsure of egsactly what to do . im sure someone will help you thow soon enough .

Alextb is right, I'm afraid - Lavender cannot be pruned hard into old wood. this is one of those plants which really need replacing every 5-7 years, although its pretty easy to raise from cuttings, to save the cost of buying each time. It also often seeds itself. You might manage to keep it longer with regular clipping, at least twice a year, taking an inch of soft foliage each time.

you learn something every day at least you got answerd jan .

If you are worried about it not seeding, may I suggest that if you have a B&Q near you, you could try their seeds section, because in my experience, mine is always stocked up on the different varieties of lavender seeds. They may have your variety, so that you can reseed.

Also, if you look in the newspapers & mags. you always can find offers for lavendars and they are not expensive, in fact quite reasonable, the only hard job for you will be digging out the old ones!

Thank you all for your ideas. As I expected I think it has reached the end of its life, I have managed to raise several seedlings as a precaution but would they be able to be set in place of the original hedge or should I put in something else?
Jan

After 7-8 years have just ripped mine out as it had come to the end of its pretty life.

Depends if you want another lavender hedge or not - I love 'em personally, worth replacing every few years, they're an absolute delight.