How you describe the blood sausage sounds like what they call black pudding here, so it's more than likely the same thing, or names that they use interchangeably.
Purple might be what they call Ube in the Philippines... they use it to make ice cream there and it's like a delicacy...
We have purple yams in Jamaica, too, but I'm not sure what they call them.
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18 different kinds of yam!? 😜
I'm not keen on yams, but I do like sweet potatoes... and yes, the ones in the UK are more orange like squash.