I've had Yokohama Avid 205/70/R15 tires on stock TR250 rims on my TR250 for over five years. They offer great dry-weather traction, are price-competitive, and look good. I don't drive the car in the rain if I can help it, so I can't comment on wet-weather performance. I can say that I have similar Yokohamas on my Mazda (wider and with lower profiles, of course) and the wet weather traction does not come close to the dry. All of my Yokohamas have shown fast treadwear compared to other tires, but I drive hard. I'll be replacing the Triumph's later this year--maybe with Yokohamas, maybe not.
I, too, like Michelin truck tires a lot, but I have not yet found passenger car/performance car tires made by them that impressed me. The OEM Michelins on my '99 VW Passat were so-so in dry conditions but a disaster in the wet. That little tubocharged 4-cylinder could spin the front tires at the slightest provocation. Fun but scary. Their tires do seem to last forever, which has also been my experience with Bridgestones.
Sounds like there's a good case for the Michelins, I just don't have any personal experience with them on Triumphs.
Regards,