And to close ....
With a 'sql' account configured on MSSQL as a 'db_backupoperator' will run a stored proceedure dumping the database to disk without an issue.

However once you are connecting via the UDF's to excecute the code, it appears that you also irequire to be a 'db_datareader'.

Teach me for thinking for myself

Cheers for the help guys ....

Shaun