Don’t know the female singer you’re referring to but
1. The place was still called the Sherwood Rooms when I saw Diamond Head and Hawkwind there in 1984 (I still have the Diamond Head ticket stub here…
https://musicintheattic.co.uk/gig-tickets-part-1-the-1980s
2. It had been renamed The Astoria by the time Notts County FC had their historic crisis meeting there in 1986 (35 years ago today infact - link here…)
https://twitter.com/magpies_history/status/1438086572784685058?s=21
3. The TV series filmed at the Theatre Royal was called R