Are you sure you want a whole hedge in copper beech? You could just have a specimen tree in copper.
If you have heavy soil consider hornbeam, very similar to beech.
Try www.futureforests.net. They do bulk orders and deliver all over the country. Drop them an email and they'll advise on whether you should use beech or hornbeam. They also do native hedging mixtures that are brilliant for wildlife and are very good value. I have no connection.