thanks to andrew's kindness I am going to be able to find my faulty sensor and sort out the problem !
in anticipation I sourced a new one from germany , arrived today , correct part number , correct connector , but it ain't right !

the actual sensor bit in the centre isn't the same shape ! it's circular instead of squared off circular ! anyway I gave it a fine emery paper , sprayed the correct colour , finished with lacquer , dried in the hot sun ...looks a treat so will fit !

Ian would have a fit !

There's a thread I've posted in that gives the correct part number and a source in Germany for pre-painted sensors to match your paint code. I bought a set of 4 for the back of mine for about £120 delivered. They sell individually too....

I suppose as I paid £12 delivered in primer I can't complain ....I had the paint /lacquer anyway ; and as I said , they had the correct part number