Next time take it somewhere that has a aluminum/mag wheel changer. The same type machine that changes tires on corvettes, sport cars, etc... I have ran one of those machines back in the day when I worked at a tire shop. If the operator knows how to truly run the machine.... there should be no scratching of the wheel.
If a car tire is installed it makes the job much harder than changing a motorcycle tire.
The bad thing about the Triumph un-coated alloy rims is that they are soft and mar easily (especially near someone who shouldn't be allowed to hold a tire iron).
The good thing is that they can be sanded and kinda worked back into shape. You can't fill in, but you can pretty easily smooth out. I could have spent more time, but this'll have to do for now.
Here's the before and after showing the worst spot- there were several. The white in the photos are reflections of the lights overhead.