Retirement & flexible retirement requests

Can I choose my own Company standard retirment age, e.g. 60, 65, 70?
I have an employee who is due to retire in a year. What must I do? (the flexible retirement procedure is now required by law)
An employee has requested to work beyond 65. Do you advise us to let him?
What reasons do I need to give to refuse an employee's request to work beyond retirment age?