Thank you all for your excellent advice (and stories!). Pondered all and slept on it, made my decision.
Looking now for a 45/70. There were many aspects to the process, but deciding factor was the range of loads available, as I will be using it both for target shooting and hunting - boar and bigger.
It won't get hammered and I have a preference for old and beautiful, rather than shiny, new or hi-tech.
No preference for straight or pistol grip, as long as it fits comfortably and shoots reliably.
Not single-shot or bolt-action. So double rifle or underlever repeater (ideally long mag but not critical).
I like open sights, but plan is to augment with red dot and if possible use both.
The final purchase will be published here and I will review performance in due course