Estel: If the core C4 state issue is not likely to be caused by a faulty battery, I might put off getting a new battery till I resolve the issue.

I've read through some of the posts in the battery thread - thank you for summarising it nicely, all over again! Unfortunately, none of the recommended batteries are available where I live. There are "original" Nokia BL-5Js on sale on the local Ebay, but I've burnt my fingers with one already. Anyhow I shall eventually arrange to get a Polarcell, once I get the C4 issue out of the way.

Next up, I intend to check the flex connectors and give the internals a close inspection (not that I'm counting on finding anything dramatic, but still).

Ancelad, coderus: Thank you. As you will have guessed, it is from a background in coding, in what already fast feels like a past life!