Do something before the food
The Christmas meal is not the problem. Three hours of only the meal is the problem. An hour beforehand gives people something to talk about that is not work, and it breaks up the group that always sits together.
Book earlier than feels necessary
December fills from about September, and Friday evenings go first. If your date is fixed, book the game as soon as you have it and arrange the table afterwards.
Mid-week in December is easier to get and usually cheaper everywhere else in town too.
Splitting a big team
Each room takes 2-6 players. Larger groups split across rooms and play at the same time, then compare times afterwards. We can take 18 people at once across the venue.
Nobody is made to do anything
There is no forced participation, no singing and no fancy dress. People who would rather watch can read things out and hold the torch. Everyone ends up involved anyway.
Getting here
Inside Laser Fusion at The Old Fire Station on Silver Street, near Broadmead.
The Galleries car park is closest; Cabot Circus is about a ten minute walk.