Decent grid although one of the rows was a bit too specialised for my breadth of knowledge.

Challenging and good fun.

nice

Good one, though the Addison line was outside my narrow field of knowledge of popular culture.

Down's disease? Really!

I think that is a real blunder,I agree! Spoils a good grid..

I put in diseases or syndromes named after people, I think that would have been a fairer answer. Don't watch the IT Crowd, so that one passed me by! A good grid. Thank you Dave and Al

Down Syndrome (not "Down's" because English physician John Langdon Down, who characterized the condition, did not actually have it -- 's connotes ownership or possession) is NOT a disease. So the inclusion in this category is incorrect in TWO ways. LAZY compilation!