Richard,
I always found Lincon, in Essex, to be good but more recently they were unable to ship because of the acid hazard.
I now use Tayna, based in Wales ….
https://www.tayna.co.uk/car-batteries/classic-car/
They offer a good selection at reasonable prices with an excellent “NEXT-DAY” service throughout the mainland. The batteries arrive very securely strapped to a pallet, presumably their way round the hazard issue.
B…..
Bernie