I'll carry on waiting as I really do require an answer.
Thank you. I'll wait for your reply.
When you look inside the connector block moulded onto the rear of the lamp assembly, the plastic around the earth terminal is a brownish colour which I take to mean that the terminal has been getting hot.I cut the wire to the earth terminal in the harness connector (the brown wire) and joined it directly to the wire I soldered to the earth frame in the lamp assembly using a screw terminal block. It didn't make any difference.