Hello George,
your original post mentions Heinkel Kabine, but as you say you are now a member of the H/T club you are probably familiar with the Trojan verson, as well as the Heinkel-Ireland one. Early Trojans had a small Heinkel bagde as well as the Trojan one. Unless you have a particular reason for wanting a German Heinkel, the other two variants are worth considering. I, like a lot of UK fans have a Trojan which are more numerous. Trojans lack a few details found on Hs, such as a clock, and the early 175 cc engine is well-regarded. Some Ts and H/Is are LHD.
The extra room really is useful. I drove a bride and her Father to church for her wedding, he is about 60 and medium-llarge size, but he managed eventually to squeeze into the back seat for the short trip. Later I took bride and groom to reception. It was a paid gig, and a lot of fun for all. The Dad has a great collection of classics, including a superb Rover P5, Daimler, BMW and even a white RR, but decided to surprise his daughter...and she loved it. Try that in an Isetta or Schmitt!
Good luck in your search.