Funny enough, I discovered parsnips here as well.(roasted ones taste good.) My weird finds are:
Korean shops commonly sell light corn syrup.
Filipino grocery shops sell graham crackers, saltines and pancake mix in addition to Lipton iced tea mix with lime
Dadu's Cash and Carry in Tooting stocks any kind flour that you could ever eat or want. They stock big old bags of corn meal in coarse medium and fine grinds in addition to very big bags of peeled and finely ground almonds Dadu's also sell Crystal hot sauce which I love and corn nuts to boot. That place is spiceheaven
Dont let the foreign shops put you off because of the languge issues you might uncover some hidden gems like big bags of popcorn and cheap coconut oil at Dadus. or Pillsbury frozen nans or parathas with the little doughboy on the package