OK, I got a satisfactory, if not perfect, result.
Couldn't expect miracles
I used Hugin and the tute I linked to get the settings right.
I needed a few nore scans to get sufficient overlaps for best results.
Yes it was while doing it I noticed that the joins had to be lateral
so essentially two banners, rotated 90 deg and then joined.
Thanks for all the suggestions and help.
I have been trying with A1 sheets also ..... but the scanner bed is really too small ... needing about 20 scans to get sufficient overlap.... and the one I am using is not as 'high' as the surrounding case so is very awkward.
I have an older unit somewhere which may be more suitable ...... but that is for another day