I received the following official communication today, contrary to some contributors here.
“Sale of alcohol on the parliamentary estate
Alcohol will not be sold after 10pm anywhere on the parliamentary estate. In line with the Government’s industry guidance, catering facilities will remain open later (but no selling of alcohol) when the House is sitting, to serve food for those still working and to support social distancing.
This decision was taken by the Speaker last Thursday. Today [28 September] is the first day since that the House is expected to sit beyond 10pm.”