I believe that at least some insurers will accept a U.S. insurance history and acknowledge it with an appropriate level of no-claims dicount, but as with all auto insurance issues, you'll need to shop around, as quotes will vary widely.
Add to the fact that I am about to buy a car - would it be better to register it in my husbands name add it to his insurance and not drive it until I have my full license? Or can I register it in my name and try to get cheap insurance? I can't really wait to purchase the car as its a rare classic car that doesnt come around for sale very often. 
If your husband already has a car with its own policy, he may not be able to just add another vehicle to it. A few companies offer multi-car policies, but most require a separate policy per vehicle (assuming you want to insure the vehicle for fire & theft etc. as well as just the legal liability cover for driving it).
There is no absolute requirement that the vehicle be registered to the person taking out a policy for it, although insurers will often ask if you are the owner/registered keeper
* and ask a few more questions if not.
There is no fee for re-registering a car to a different person here, so whoever's name you use when buying it now can be changed easily later if necessary.
By the way, what sort of classic type/era are we talking about? Insurance on older classic vehicles can be surprisingly cheap, unless it's something worth an exceptional amount of money.
* Note that DVLA does not record who actually
owns a vehicle, only who "keeps" it (i.e. the person considered responsible for taxing it etc.). So in fact the registered keeper shown on the V5C registration document does not necessarily have to be the legal owner.
