There is no need to change the standing orders. This is a prudent public health decision for a single meeting, with the option of repetition for future meetings. The operator of the building must have an up-to-date Covid risk assessment and Covid-safe policies and procedures. If these state that masks are required, there is no option, apart from those individuals who have a valid exemption. If the operator doesn't require masks, individual user groups may still do so.
The challenge we face with Omicron is that many people who have it are unaware of that fact, which explains the huge number of cases we are seeing. My village halls and community centres are still requiring masks for all events and activities, as case numbers in our area remain high. We must all play our part.