Once again, thanks to all contributors. As Ray Padgett says 'the plot thickens'. I've been otherwise engaged over the last few days and unable to follow this subject up but have a day or two off work and hope to make further investigations. I shall contact the company called Dudley (at Dudley in the Black country) and other possible sources that you good people have indicated. Hopefully I, (or we) may be able to find an answer and I shall be able to sleep easy in my bed at night afterwards.