We don't have many hedges here in NE Scotland, fields are separated by fences, or stone walls, or conifer woodlands. There are a few beech hedges around, but not many hawthorn, although it seems to grow ok. As my family roots are in Leicestershire, where there are many miles of hawthorn hedge, I decided a few years ago to start planting hedges around our somewhat exposed farm, to provide shelter and make it look nicer.
So, I think 5 years ago, the first stretches totalling maybe 800 metres, were ready for their first trim. I found a local contractor with a modern flail hedge-trimmer, and he came and did them. The bill was £300, 10 hours @ £30/hour, which I thought was a little steep, but he made a tidy job. The following year he had some heart trouble, and was unable to work; last year I found another contractor and he agreed to come, but did not appear before the end-February deadline.
So in exasperation I decided to get my own machine to cut our now overgrown hedges. I thought a cutter-bar machine would look good on my Major; of course none were available locally, and via ebay I found a McConnel in Oxfordshire. It had not been used for a long time, and did not have a drive-belt; but I got it brought here on a pallet, and it seemed ok. From a separate ebay listing I also got a user manual, dated 1965 (!).
Our local Ravenhill (New Holland, and McConnel, agents) tried to get a belt, but McConnel can no longer supply parts for such an old machine. I tried a couple of conveyor-belt suppliers, but none seemed interested in supplying a 14-foot x 3" belt. So I went back to Ravenhill, and asked about belts for a round baler (we used to have a Farmhand baler, which I thought used similar belting). Success! I had to ask their workshop to fit a joiner, as I had sold the joiner-fitting device I used to have, when I sold the baler. But the total cost of the machine, transport, the belt, and a new hydraulic hose, was about £400, which I am happy with.
With some trepidation I fitted it to the tractor (I had to alter the top-link bracket, according to the book there are different brackets for different tractors, and I think mine came with a bracket for a Ferguson or 35). I do not have the optional hydraulic angling kit, so I have to set the angle of the cutterbar with a pin, then alter the height using the tractor's hydraulics. The tractor's lift arms do not move, only the arm of the machine. I guess if the field was bumpy it would be difficult to cut the hedge straight, as the tractor would be tilting, but that was not a problem here.
According to the book it can cut up to 40mm/one-and-half-inches branches; the blades are similar to mower blades, triangular, but with saw-tooth notches at the tips. I did most of the hedges in 1st gear, briefly pressing the clutch (the tractor has live-drive) if it got hold of a thick branch. But I would think that next year I will be able to use 2nd gear, and I can't see the whole job taking more than 10 hours. So I am happy.

I can't post photos of the actual machine tonight as Imgur has frozen; so here is a photo I found on McConnel's website. This machine must be even older than mine as it doesn't have the shear-bolt breakaway to protect it if you hit something.
https://www.mcconnel.com/_i/w/1200/h/68 ... versal.jpg