I've always had a hankering for a little grey Fergie myself.
I have absolutely no use for one, and never have had, so I've never really understood why.
Re the pellets in the fuel tank. When leaded fuel was effectively abolished*, the classic car buffs were understandably concerned about their engines.
An official organisation of some sort, I forget which one, tested a good number of the proprietary "solutions" and proved they were indeed largely snake oil.
The Advertising Standards Authority then banned most if not all of the catalytic systems as being cobblers.
There are half a dozen or so approved liquid octane boosters but as far as I know nothing else has ever been proven to work.
*Not quite abolished but if you find one of the few garages that stock it, the price is astronomical!