The other exception to your short dim sum menu rule is the ultra-posh places (granted there aren't too many of them in blighty) but some restaurants in Hong Kong and Singapore have quite short menus. However, it's obvious that they're hand made as they tend to use posh ingredients.

And yes, I am so with you on the terribly aberrant practice of eating dim sum after hours. It's just wrong.

PS: Thanks for the link too.