The only bike shop I've found within a reasonable distance with a tandem to test ride actually had two tandems, but both were Cannondale MTBs!

I have a good relationship with my LBS, so as long as the frame isn't a noodle I should be fine; they'll swap out pretty much anything I manage to break - I know from experience

In the '70s, Dawes bike were made a little way away from me in Tyseley nr. Birmingham. They're made in the far east now, but I wonder if the bikes are still assembled there.