Thanks for the thoughtful and thought-provoking replies
My situation has changed somewhat as originally I was trying to repair an old HP A3 printer and as one of the printheads was toast plus the fact that HP discontinued ink stopped me pursuing this course of action. This decision leads me to consider a printer purchase and looking for the facility to print A2 I looked into used models. A Canon IPF5100 and HP ? came up at very low cost (compared to new) and in considering such I felt it important to understand the workings in more depth than perhaps buying a new warranted item, hence my search for service manuals and my first post.
After much thought, I changed my mind and decided to buy newer technology, the choice between Epson P800 and the Canon Pro 1000. Decided to opt for the Epson P800.
As to the legality, it does seem that there is a breach of copyright as the manuals are not revamped from the original service manuals (similar to other service manuals e.g. Haynes automobile comes to mind) but direct copies. Funnily enough at least from my understanding, someone could teach me using the original manual as the syllabus and their own reworded manual from the original without any legal consequence.
On balance without any deep thoughts on this subject, I do tend to agree with those that argue against companies perceived to be "hiding behind copyright law". For me, at this time it is a moot point anyway due to the arrival of a new machine.
FWIW a couple of examples of others thoughts on this
Let me make one thing clear: copyrighting repair manuals doesn't protect creative work and it doesn't prevent knock-off artists from copying design. All it does is stop people from fixing their things. It prevents independent repair facilities and shops from having the information they need to repair your stuff at competitive prices. And it prevents refurbishers from having the resources they require to fix products and put them back on the market.
Without critical repair information from the manufacturer, more and more of our goods will be shredded for recycling or worse, simply thrown away to make up part of the 1.37m tonnes of e-waste Britain disposes of each year.
https://www.wired.com/2012/11/cease-and-desist-manuals-planned-obsolescence/https://www.theguardian.com/sustainable-business/copyright-law-repair-manuals-circular-economy