The French Culinary Institute in Soho is an amazing place, with all kinds of classes from short classes of the type you are thinking about, to full-time professional chef courses. I did the week-long 'artisanal bread baking' course there a year ago, and it was a life-changing event! There were a couple in the class who were there because of gifts from family members. Another who came from Nigeria. Another from Japan.
And the great thing about the FCI is that it's in Soho, which is easy to get to.