I'd appreciate any suggestions on which MF Rangefinders there are - I haven't a clue!
Not sure these would work for you, but consider
Mamiya 6: very limited selection of superb lenses in a clever collapsing compact body of somewhat uneven build quality. What you'd think is the weak point -- the collapsing lens mount -- is actually very well done and quite sturdy. What you'd take for granted they'd get right -- like the film wind -- somehow feels a little fragile. And why doesn't the rangefinder base take up more of the body width, Leica M style? Not cheap.
Mamiya 7: the 6 plus even more excellent lenses + 1 cm film + still in production - the collapsing lens mount. I still like the 6 better (now if the 7 had a collapsing lens mount ...) Definitely not cheap.
Baby Tech/VHR/Century Graphic: Old, kind of clunky, the Linhofs are quite heavy, the CGs pretty light. But movements get addictive, there's a huge selection of lenses (though most have to be used on the ground glass), and at least as far as the Linhof goes, the joy of something really really well made. CGs are quite cheap, VHRs rather pricey, Linhofs alas ...
Is the next question: what's your favorite LF camera?