Thanks for all of your kind comments. You can probably tell from the shape that I made the cutters from a spare mortise lock striker plate, this reduces the amount of cutting required. These are quite time consuming to make accurately using hand tools. In a production environment they could be made much more rapidly using CNC machining systems and presetable repetitive punching jigs.
The only ready made tool that recognises this access difficulty is sold by Laser Tools, this is a double jointed side cutter whereby the operating levers take up a bit less space than the handles but this tool still does not allow one to cut sideways at depth.
https://www.lasertools.co.uk/product/6969
Neil