Found an article in TheGayUK from October 2015 that lists London LGBT bars that have disappeared since 2000. I am listing the bars that are specifically identified as lesbian below. Some have been posted on here before, some have not.
The Blush Bar: a lesbian bar in Stoke Newington. 1997 - 2015.
Candy Bar: London's number one Lesbian bar - had a brief reopening, but closed again in 2014. 1996 - 2014.
Lounge: Iconic lesbian night which closed then reopened then closed again.
Rush Bar, a lesbian bar which closed in the mid 2000s.
Southopia: a lesbian bar in Kennington.
Stokey Stop: a lesbian bar in Stoke Newington
Interesting that four of the bars listed above (Southopia, Blush Bar, Stokey Stop, Rush Bar) were not included in the original article--which is wholly dominated by male venues--but had to be suggested for addition by apparently female (lesbian?) contributors in the comment section. So even though lesbian bars are rare and getting rarer by the moment, the queers and gay boys still couldn't manage to identify and include the few that existed without being prodded. Very typical as these things go.