[peter_scott]

I did look at the possibility of an electrolytic but saw that it would be reverse polarised on part of the cycle so I fitted a non polar 400 volt cap. I've now added a couple of 0.1 uF 1000v caps and I must confess that it does look much better.

I think you and David have just saved me from further fruitless going around the houses.

Very many thanks to you both.

Peter