https://www.virginactive.co.uk/the-legal-stuff/club-rules
"By law, our members and visitors who use a changing room marked as ‘male’ or ‘female’ must select the one that matches their biological sex.
Our unisex and single-occupancy facilities can be used by everyone, and we are updating our signage to ensure these spaces are clearly marked and easy to find."
I assume there will be a lot of these changes happening in the very near future, and the guidance is about to arrive if we are lucky. Do not think Virgin would put their head above the parapet on their own.