Yes, Pete (like most things of value in the biomed world, it seems), those suppliers are all in the States. I really included the links just to make "others" aware of what we were "talking" about, some of the possibilities
vis-à-vis replacement batteries, and the engineering involved. Perhaps some enterprising souls in the UK (are there any left? ... please discuss) could have a go!

PS: it just amazes me how many batteries some of those modern mobile (not "portable") x-ray units need. There
has to be a better way!