Draper's Mill, Margate is open I believe, this weekend (9th 10th) for SPAB Mills Open Weekend.
Anything that attracts visitors to Margate can only be good news.
Best call and check opening days/times first though.
I think it's Sunday:
National Mills' Weekend Sunday : 2.00 to 4.00 pm
More info:
http://www.joylandbooks.co.uk/forum/vie ... php?t=1829
http://en.wikipedia.org/wiki/Draper's_Mill,_Margate