Age limit on car rental

There is no legal limit. It is up to the rental company and their insurance companies whether they will accept you, charge a surcharge or say no. If one company says no or charges too much, shop around.
If you have a British licence, if you are over 70 you need a doctor's approval to renew your licence.

Although it is illegal to discriminate in terms of age, you will in practice find that it is more expensive if you are over 70 and again if you are over 75. The best thing to do is to get a few quotes.

You do not need a doctor's approval to renew your licence here if you are over 70, as you self-certify, so the previous post is incorrect.

My father was renting cars in England and Italy in his 80s.

Small company in the UK, Avis in Napoli.

Are you counting on your husband to drive, or will you drive all or part? If both of you, then both drivers have to be named on the rental booking.

If you can use a car from three weeks or more, older drivers find less resistance through a leasing program like http://europebycarblog.com/ or http://www.autoeurope.com/buyback.cfm. These cars can't be picked up or dropped off in Ireland.

In Ireland, Dan Dooley's age-selector pull-down options go up to age 99: http://www.dan-dooley.ie/.

Laura is right about the advantages of a lease if you will be using the car long enough. There is only one draw back to the lease plan. All of the leases exist because of a loop hole in the French VAT law and will ultimately be resold as used cars in France. The result is that you will be driving a left hand drive car in a right hand drive world. Two years ago when we were 73 & 71 we had a lease car for three weeks in the UK & Ireland with no serious problems. All you really need is a good front seat navigator who will occasionally shout "KEEP LEFT", most commonly after making a right turn. There are a great many advantages to leasing, among them are; 1) The only age restriction is that you are over 18; 2) You can absolutely take the car from the UK to Ireland with no restrictions. Have a great time.

Good points, Irv. When I picked up a French leased car in London that one time, I actually enjoyed being in a left-hand drive car, since did not feel so close to oncoming traffic on narrow roads. On the downside, as a solo traveler sitting on the wrong side of the car, I had a hard time paying at toll booths in parking lots and such. I also took my leased car on ferries to Ireland and back, which regular rental companies often don't allow.