Some good online old map sites:
https://www.sabre-roads.org.uk/maps/
https://maps.nls.uk/geo/explore
The latter of those two links has given me hours upon hours of pleasure.
Mentioning it to my my neighbour resulted in her memory going "zing" and rooting out a 1915 Caernarvonshire XXVIII.2 25" and 1900 Caernarvonshire XXII.15 25" maps (where we live) wot were rolled awfully tight in a tube and had lived in her loft for many many years. (Paper size: Grand Eagle 28¾" x 42")
These were missing from the
www.nls.uk collection. So I contacted them to see if they were interested. Yes they says please please. But warned it might not safe to post it to them - in case it got lost or damaged for ever!
I found a local place in Porthmadog who could scan A3 for £12. But when I emailed the resultant B&W .pdf to
www.nls.uk it didn't meet their understandably strict and specific requirements to include it on their interactive data base.
They then provided their scanning criteria, but the shop in Porthmadog couldn't do colour and the very specific colour profiling to meet the NLS needs.
I hope one day to find another printer locally who could do the biz according to NLS spec - or find myself going to Glasgow in person.
It is after all a fab city
ps both maps helped me locate and uncover (literally, as grown over in ancient moss), 2 x Ordnance Survey benchmarks, not listed in any current online records