Cracked it.
To bypass the lock press the PP key 3 times. The lock can then be switched off via the normal menu option. (Press menu 3 times then select Function and Key OFF)
Got the detail from a Tantung user manual at www.tatung.co.uk-user_manuals-t14tk73js_umanual.pdf
I did try Aldi who true to form could not help.
Steve
November 2007