Thanks for your replies.
I have used YES VM internally as well as externally on nights that I don't use a hormone treatment - can it stop the hormone being absorbed?
No I would say its ok to do both, I use Yes moisturiser when using Ovestin (Estriol) and it doesn't seem to have any effect on its efficiency.
Perhaps try the WB Yes, I can't tolerate the VM one, it irritated and made me sore but I'm fine with water based.