Many thanks for all these helpful replies. I have fired it up now and am gently probing its capabilities. As our existing Windows machine is still very capable we are going to take it slowly but surely as we transfer over to 'Macland'.
I am giving some consideration to backups etc. I am cautious, probably too cautious, over nefarious scoundrels entering the house and taking not only the iMac but any backup drives or hardware hanging onto and around it. I was hoping to be able to back the whole thing up to the icloud on a regular basis but I gather this is task too far. I was thinking of backing up (with Time machine?) perhaps to a wireless NAS drive that I could hide away in a very unlikely to be found place. I am paranoid I know.
Can the team give me any advice or personal experiences with their failsafe backup procedures? I appreciate the time you've given already.