I've done a bit of fiddling around with testdisk and photorec, ended up with an image.dd file of about 46~48mb like before, as testdisk seems to think that's how big this 2gb card is. Both programs seem to be telling me there's 0 files on the card, and testdisk can't locate any partitions. It can't find anything at all unless I select 'none'.
I'll happily admit I'm very much unsure I'm doing as you recommend correctly, but this is just lending further credence to my "this sd card is just completely busted and unrecoverable by me so may as well just get another one and start again" sort of deal.