Ok, all the new plugins that the client had added are now deleted, but still no Mail data showing.
No success with the serialization fixer script either (sure did fix a lot of other serialized data in that table though!!).
Just to confirm, in the database, the meta_keys for CF7 have an underscore in front of them
_form _mail _mail_2 etc.
I notice some meta keys don't have the underscore, so thought I'd ask...