Seems my assumption was wrong, or only worked on my specific card that was failing to init. I guess I should try with another couple of cards, but it will have to wait some time as I'm only a hobby maker so have to budget the expense. Might be worth me getting a range of sizes (my card is only 4G) to see if that makes any difference. I used the micro 4G specifically as it was cheap and had been sitting at the bottom of my "I'll never use this; but will keep it just in case" draw for years after I'd fried the 32G card
.At least we both have a partial resolution to the issue.