Thanks, I'd previously cleared the cache but not the storage, to no effect. However I've sat for ages retrying this and after a million or more fails suddenly one worked - nothing had changed (except my mood!!). Unfortunately I'd become so mechanical I didn't really register whether it said Failed but I suspect it probably did.
And now I'm loath to change it back to see if it really does work LOL
As I mentioned I did a report to MG. I can't imagine for a minute they'll act on one persons report but you never know. I don't think there is anything else to prove or try - but thanks for your assistance, really appreciated. If I ever get any answer I'll post it here!!