It is still in there. I tried 15 minutes at first and as expected, I could access it again, as per when it was cold first thing this morning. I then tried about 3 hours and same again, so I put it in again at about 5.00pm this evening and it's still there now. I've not been any further into it than I had but at least I know making it cold makes it accessible, although doesn't help with the corrupt aspect of it.

Some guides I read suggested 12 hours.

I reckon software will sort it, it's just working out what will work. I'm trying the ones that have been suggested above and will keep you posted.