The plastic knobs seem to shrink with time and grab the shaft rather tightly. When I helped a friend with his TR6, I actually asked him first if it was OK to break the switch because it took so much force! But, by using a pair of pry bars, one on each side, with a scrap of wood underneath to protect the panel, I did get the knobs off without ruining anything. Some quick work with a needle file made them fit much easier.
IIRC, on a 69, the dash mounted ignition switch has two notches in the bezel, similar but not quite the same as earlier cars. I machined a piece of water pipe to fit the two notches, to allow the bezel to be unscrewed without too much damage. It's tempting to just stick the tips of needle nose pliers in the notches, but my hands haven't been that steady for a long time, and plier tips can do a lot of damage when they get loose.
On the later column-mount switches, I don't recall the chrome coming off separately, but that's probably just my memory. It has been awhile.