Can anyone help me with how to write a retirement policy?

We have a clause in our handbook which states the normal retirement age for employees is 65, however, historically, people have been allowed to work beyond this age depending on the skills they have.

When I first started with the Company we lost a tribunal in forcing people to retire, because they were all women working part time – sex discrimination!

I have been asked by the Financial Controller to look into forcing people to retire, however with the new legislation coming in in October, I am not sure where to begin.