I think I have real problems with applying different rules to men and women where social policy is concerned. If it is wrong for a woman to become a mother over a given age (presumably you mean by surrogacy, IVF or adoption) why is it right for a man to be treated differently? More particularly, given you seem to argue gay couples should be allowed to use surrogacy when older than straight couples, does this apply to lesbians in your argument (given what you have said about mothers?) See the difficulties? This would amount to (unlawful?) discrimination on the grounds of sexuality. ! have a lot of sympathy for gay couples who want to have a family life caring for a child but they do have choices other than paid surrogacy routes, such as adoption or fostering. I know professionally and personally many fantastic couples and single gay men and women who are wonderful care givers to children biologically unrelated to them. That doesn't mean that we should sanction paid renting of women's wombs (usually in third world countries for people who don't have Elton's wealth and influence).
So you don't agree with surrogacy full stop, or am I just being obtuse?
What if a gay couple want a child that is a part of their genetic heritage and don't wish to adopt or foster? It's very difficult for gay couples to do either from what I've heard. Your gay friends must live in a very rare local authority area where they are very willing to let them foster or adopt children.