Where can I get reclaimed stone for a wall

We are thinking of building a stone wall in our back garden that we can use as a suntrap for growing fruit trees, vegetables etc, our inspiration being the walled gardens in Farmleigh and Marlay Park - those walls look fantastic. I was wondering if anyone out there would know where we could buy reclaimed stone at a reasonable price. Even though it's recycled, I've heard it can be expensive as the stone is hard to get, it has to be collected, old mortar removed etc. The wall we want to build is about 10m long and 2m high.