Would you use "vapourise" or "vaporise" is British English? Thank you!
According to most dictionaries "vaporise", "vaporising", "vaporisation"...etc are the forms used in BrE, but I've also come across "vapourise", "vapourising" and "vapourisation" as well.
Is one form more correct than the other, or are they both considered correct?

Question

Would you use "vapourise" or "vaporise" is British English? Thank you!
According to most dictionaries  "vaporise", "vaporising", "vaporisation"...etc are the forms used in BrE, but I've also come across "vapourise", "vapourising" and "vapourisation" as well. 
Is one form more correct than the other, or are they both considered correct?

Answer

None of the variants you mentioned are Oxford spellings, which use -ize rather than -ise.

Vaporise is correct, though I think we would prefer 'colourise' to 'colorise'.

The inconsistency with vapour/vaporise is usually taken as reflecting the French origin of the words (vapeur and vaporiser). 'Colourise' is a modern invention, which is why it seems to make more sense.

Answer

The forms with the 'u' are wrong, even in BrE. 'Vapour' is correct, all the derivatives lose the 'u.'