Ok, I’m not sure what just happened, but everything has just come back.
I had just made some changes to the network controls (marking 192.168.1.0/24,10.0.0.0/8 as LAN, and not needing auth) but changing those back to what they were originally didn’t make any difference - I can still see all my shows and DVRs again. Not even sure this is relevant, but mentioning for completeness.
In any event, everything is back, including the poster-images 
