@simon_lucy I see. I think the confusion arose because OO can have multiple pronunciations: the one of 'foot', 'wool' etc. and the one of 'goose', 'doom' etc. I used the 'Wooster' spelling, the way the surname that's derived from 'Worcester' is spelled.
@yvanspijk
The vowel sound in English might seem detached from the spelling but it isn't. The pronunciation tends to be consistent for the same word, wool is generally wuhl within the range of the accent but wooly, to have the nature of wool is more extended it kind of falls between uh and oo.
But someone from Liverpool would likely pronounce book and cook as BOOk and COOk, though personally I never did.