OH and I did a course a few years back - it's wonderful, far more skilled than you would at first think and immensely satisfying. Each area has its own style so now when we travel around we are constantly admiring walls
What we haven't yet done is to repair our own short section of drystane dyke, which is why we did the course in the first place
I'm sure that if you do a google search you will find courses. I think BTCV (is that the right acronym?) run them, but also maybe agric colleges. There is also a drystone walling association.