I wasn't around the folk scene then, so I can't speak from personal knowledge but the advertisement I cited came from here:

https://nationaljazzarchive.org.uk/explore/journals/jazz-news/volume5-no37/1275906-jazz-news-volume5-no37-0010?q=ottilie%20patterson

If you can get the link, the advert is at the bottom of the second column on the right-hand page. It's not easy to read but, in the bottom left-hand corner of the screen there is a "+" sign which, if you press it, gives a 'magnifying glass' effect allowing you to read the detail more clearly.

The advert refers to "sessions" - two on the 16th September, two on the 23rd and one on the 24th. At the bottom of the ad, it says, "Thereafter, Thursdays, Fridays, Saturdays and Sundays".

The location had, of course, previously been The Partisan coffeehouse but the advert does refer to "sessions" (and not, for example, "opening hours").

As I mentioned earlier, SING thought the club would reopen, after the summer break, on a Saturday only (but erroneously gave the ACTT premises as the location, which you corrected). In its November 1961 issue, SING provided the following details: "Sat. 7.30 and 11.00" and then added "(Open Thurs., Fri., Sat., and Sun. from 6 p.m. as a members' club)".

I can only report what I've found in contemporary publications, I'm afraid.