Hope this helps...
From Rick Steve's site:
While age limits vary from country to country and company to company, those who are at least 25 years old should have no trouble renting a car. (Younger renters can get stuck with extra costs, like being required to buy CDW insurance or pay a "young driver's surcharge.") Most companies will not rent a car to someone under 21. Only Ireland has a maximum age limit (75), but some car-rental companies enforce age limits of their own. If you're considered too young or too old, look into leasing (see below), which has less stringent age restrictions. STA Travel seeks young renters (
www.statravel.com, tel. 800-781-4040).
From another site:
We will be 78 years old when we next visit the UK and Ireland. Is there an upper age limit for renting cars in those countries? If rentals are not an option, can we hire a car and driver?
A: It used to be that upper and lower age limits were prevalent in the rental car industry throughout Europe. Lower age limits still exist almost universally, at least among the major rental firms, although some firms will rent to under-25 drivers for an additional daily fee. Upper age limits vary with the rental company. Avis, for example, has no upper age limit restrictions in Europe except for Ireland, where the age limit is 74. Europcar has a 69 age limit in Ireland, and 74 in the UK. Hertz has no upper age limit in the UK, but a 79 limit in Ireland, so you’ll just squeak by. If you decide not to drive, most rental car agencies can arrange a car and driver as well, or your hotel can arrange one for you.
http://www.drivetravel.com/carlease/index.shtml
