I live with my Israeli wife in England. She wants to take the children to visit her parents for a holiday. I don’t want her to go for too long. Does she need my permission to go?

No, as long as she does not leave England for more than one month. English law generally allows a parent to take a child out of the country temporarily for up to one month without the permission of the other parent, even though where they are married he has equal and joint parental responsibility for the child. So, make sure that her return tickets are within one month. If she stays longer than one month without your permission, this would be a case of a ‘wrongful retention’ under the Hague Convention, which allows you to take proceedings for their return.
Preventing Abduction