Hi,
I thought I'd post about our recent travel experience in case it's at all useful to others! We travelled LHR to ORD and back on AA/BA with two USC and my UKC spouse. He has a B1/B2 visa and this actually made the experience at Heathrow very straightforward. Unlike an ESTA, his visa was not cancelled and after showing the BA employee our marriage certificate we checked in as usual - no calls to CBP to reinstate ESTAs needed. We did see a queue of people having this done and then spotted them again at the gate, so as long as you are at the airport in a timely fashion with your documents, all will be well. We used VeriFLY and this was super-useful to show documentation such as tests results etc - took just seconds both to and from Ohare. We were never asked to show hard copies of anything, though I did have these with me.
At Ohare my husband ended up in secondary inspection for over an hour (grrr), but this is normal for him due to the reason for his visa. They never actually talk to him and nobody cared about seeing any documents etc. We spotted the other UKC spouses just going straight through. Lines at immigration impressively short!
Departure from Ohare was easy - again used VeriFLY - and very fast UK entry through the automated gates.
For testing we used:
Express Test at Heathrow for PCR (I know the US only needs antigen test....) and results were back in less than 24 hours. We live not far so just went along to get tested in the evening 3 days before the flight.
C19testing.co.uk - antigen tests to take with us for UK entry. They don't need you to do the video appointment so this was convenient and the certificates were accepted by VeriFLY.
Testing for All (day 2 tests) - These are due to arrive tomorrow. They are a very reasonable price at £48 and you can return via a Royal Mail priority box which is handy for us. Not that fussed how long they take since we don't need to quarantine!
Hope that helps someone!