Wedding Marylebone Town Hall

My wedding is taking place at Marylebone Town Hall in May.
Has anyone else married there before or have attended a wedding there.
Not sure on timings arrival, think service is 20 mins. Have elderly relatives who can’t do the steps. there is a separate access but how does photographer take photos with guests unable to manage steps. Still have option of marrying at our wedding reception Home House in Marylebone. Have 70’guests , 8 bridesmaids. Wondering now whether 70 is too many for Marylebone Town Hall. Having to hire a vintage red bus from Home House on Portman Sq to take guests to Marylebone 6pm ceremony Town Hall even though 5 min walk. Any advice would be greatly received. I have no wedding planner so doing it all on my own