Some feedback for anyone running into this post. I ended up buying an Akita electric pole saw. A manual saw may be OK for regular pruning jobs but pruning four three year old growths of hazel on a steep embankment using a manual pole saw is not a sensible thing to do. The Akita did the job really well. I have to admit that the power cable is something of a nuisance and getting it up the embankment (I had to prune some of the trees from the top) was no easy job.

Something of a non-sequitar - up until now I had looked upon our hazelnut trees as something of a nuisance. I saw them growing on our embankment and knew I had to deal with them one day and it always bothered me. Now that I have pruned them I realize that they are wonderful little trees. The birds love them, the wood is fine grained and workable (I have kept most of it)... . In three years time I'll have to do it all over again but they are doing a great job of holding our embankment in place.