Unless they are certified seed potatoes, you really shouldn't buy potatoes from the supermarket for planting. You have no way of knowing what viruses they may be carrying.

I can't think of anything I've got that I wouldn't buy again. My kitchen is a seventies style one which is good enough for me, no electrical jobbies that I hardly ever use except for a soup maker that my OH wanted but now he's in a nursing home and I don't use it, plus a chip pan that I don't use. 

A fair amount of fruit & veg gets growth suppressant but I didn't expect spuds did given the state a lot are when I get round to eating them.  Get to the supermarket and buy some organic ones.

That's a great point re storage Aidy, this year however, mrs R and myself arent storing any as we're not eating potatoes (keto lifestyle).
I'm just growing them for family to use as and when they're ready, I just don't understand why half grew and half didn't, could they have been treated with something to prevent them growing as normal?

Thanks. I have pulled up a dozen or so. Most are whoppers, about 3" diameter so I'll follow your routine with them