Yep there are a number of official and unofficial singing sessions, noted above ~ official sessions and others can take up to 2hrs to get a song no matter who you are!!

The Star is I believe back as singing venue after many years, also depends on the time of day and inclinations of singers and musicians to have a session!

Black Horse, Middle Earth, Elsinore, Little Angel, indeed many of the pubs welcome people to play, sing etc

Ray