What rights do I have in regards to seeing my grand children?
I don't get on well with my daughter in law and have to plague my son to see my grand children

Grandparents rights vary by state. You need to supply the state for us to help.

I can tell you, that if you do have rights and your daughter-in-law will not allow you visitation, then you would have to go to court to enforce those rights. Adn I doubt if that will endear you to your D-I-L. Maybe you should work on why you have problems with her.

I live in the uk and its not all the time my d-i-l is like this but hen she is in a mood there's no talking to her. I've baby sat for the kids loads of times but as alays walking on egg shells trying not to upset her

The UK, apparently, doesn't have much in the ways of laws for GP rights. There is an organization that promotes them:
Grandparents Apart

I also found this site that says the courts will honor them to some extent:
Grandparents Rights To See Grandchildren Grandparents Legal Rights Uk

But it appears that your son would have to bring court action.

I suggest that you are better off trying to work (maybe through your son) to develop a better relationship with your D-I-L rather then seek redress from the courts.