Update on this - I tried various combinations of lenses on each camera (thanks for the suggestion, @stetie@mastodon.social) and have achieved partial success! Turns out that the S2's problem with the red screen was due to that particular lens. The camera is (once I'd worked out how to turn off all the annoying "let me do this for you" prompts) absolutely fine. The S1 is still refusing to let me into the menu. The fact that the lens is fucked is not a problem, it's the standard F11-27.5 lens that comes with the body so I have a spare. And I never use that one anyway as I have a really impressive F30-110 zoom that looks like nothing externally and which is consequently ideal for street photography, a nice prime lens and a very expensive fish eye lens that I've almost never used with these cameras cos I bought it in late 2019... So now all I need to do is work out what I did with the other S2 battery(s) and set up the project I actually wanted my camera for in the first place (taking photos of myself before I take the plunge and start cutting my dreads off!) Unfortunately this would ideally involve inserting the WU-1b wireless adapter that I think killed the S1, so not sure whether to do that or just use the timer and run around a lot!