Thank you for the advice on this I do value it as I know so little about Yorkies.
Last night was the first night they had been locked in the cage and
I can report a successful night as I got up this morning to a clean crate nothing even on the pad. Now I know this may just be a one off but it is encouraging I think.
I went to the crate expecting to see them bounce out to greet me but no....they just lay there snuggled up and I had to dig them out to go potty in the yard then they went back to bed and so did I........