My husband and I visited Duxford maybe ten years ago, while on an independent driving trip through England and Scotland.
Great Experience - we have no personal connection, as do you, but are fascinated by anything to do with WWII and England has a lot to offer. Since you will be in London pre-trip, I'd guess that you can find a day trip which will easily go to Duxford, which is close to Oxford. If you have not yet looked at the Imperial War Museum website, do so. Duxford is part of this museum complex, and there may be a suggestion from this excellent website.