Thank you again to everyone who helped me with this. Banner replied weeks later confirming what Derek had said ie that the battery I wanted was no longer available in the UK.
Onecal - I contacted the German supplier but they said "Good day,
Unfortunately, due to the dangerous goods law, we cannot ship lead-acid batteries abroad."
So, after looking carefully at the Yuasa, Varta and ABS batteries that had been recommended, and careful measuring of the space the batteries are to fit into, I went with the ABS battery that Alan B suggested. It is maintenance free, virtually identical in size, and had more power than the other batteries of that size. Value also came into it as it was just under £90 each delivered.
Thanks again to everyone for your support.
On the car battery for my mother that the garage said was unserviceable, I used my charger in repair mode and the battery seems fine, for now, anyway. It was a small Yuasa 40ah battery and the garage had quoted £180 for one.
I could get one from Tayna, should I need to, for under £60 delivered!!!
Best Wishes
John