UPDATE:

Found half a solution so I am posting it here in case it is useful for anyone else.

I have created a synonymn for the table

CREATE SYNONYM [dbo].[MyTable] FOR [Dev].[MyTable]

You can't see in the synonym name in the SCD wizard, but if you edit the SQL command by hand and replace [Dev] with [dbo] then the component seems to run just fine.

It's not great as it relies on being able to create the synonym with the correct schema and anyone who edits the package in the future needs to know that the SQL has to be edited by hand if the component needs to be re-created, but it gets me out of a hole for now.

Obiron