Thanks to everyone who replied with advice, in the end I gave up trying to save the data already on the disk and set it up from scratch. The new Pi is so much faster it didn't take long to re-copy anyway. Also, thanks to the case fan it doesn't overheat and crash like the last one when handling a lot of file transfers.
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Phil Thane
Tweet @pthane www.pthane.co.uk 01767 449759 07582 750607