Contact a local tree surgeon. They have equipment that can rip it right out, and dispose of the hedge. I had mine done - it had been established 40 plus years, yet only took half and hour and cost �60.00 - worth it for not cutting it any more.
If it's a really old hedge you'll probably find the roots go very deep and you will not have the equipment for digging them out completely. You will either be left with irritating thick roots below the surface of the soil which makes growing conditions for other plants, or spend a week in bed nursing a bad back. from all the digging and pulling. I think Postdog's solution is the best. Contact a tree surgeon who will have the right equipment and the facility to take all the unwanted rubbish away afterwards.