The RHS don't seem to think woodlice are a problem! Are you sure it is lice not slugs/snails?
There was some info about them liking it warm and wet but you can hardly dehydrate your growbags, can you?
I am wondering whether you might need to get a killer product of some sort if it IS woodlice. One site said they can attack small seedlings but I haven't seen mention of them eating potatoes (though I also saw them called potato bugs!)
I don't know that it's woodlice, but I can't see anything else suspicious (not sluggy or anything), and there are millions of them. I've read various things that suggest that they'll happily join in if there's a minor slug invasion and eat everything once a hole's been made.
I'm keeping a very close eye on the squashes etc (apparently sometimes you cut them open and millions of woodlice pour out if you have a problem with them. Bleurghhhhhh), but most of the hardier crops like beets and cabbages appear to be surviving.