All of the larger car rental firms (Budget/Avis, Hertz, Alamo/National) have separate rates for rentals booked from abroad, usually termed the European Retail Rate. Those are all inclusive because the insurance carried in the UK or Europe doesn't cover car rental.
In the US, insurance is always extra, and generally more than the actual daily rental rate. The 'comprehensive' cover is a true rip-off. If you are resident in the US, you are typically covered by your own auto policy or even your credit card. In all the years I rented cars on business trips, I only took the additional cover a couple of times, once when I was too young and dumb to know when I was getting a 'hard sell' based on fear. Alamo got zapped for that years ago, but that's another story.
Anyway - if you go with Avis/Budget, rent here and get the better all-inclusive rate, and check if there is a charge for an additional driver. Likely there won't be for a spouse, but if it is, the charge will be miniscule. They need to see the full UK license, including the paper 'counterpart' for the person renting. They've never asked to see DH's license.
For anyone following another thread about getting or not getting a UK license, this is yet one more reason to do so.