Over decades have been lucky to spend a number of Christmases in London.
The city shuts down. In the 70’s I was stunned by this reality. Now used to it and actually enjoy the calmness.
First bit of intel is that there is no public transport, Thus no trains, no underground or buses on Christmas Day. Now with uber you could arrange transport but expect to pay premium prices.
Stores will be closed. ( Harrods, Mark’s and Spencer, Selfridges, Liberty, etc)
However, due to the ethnic diversity of the populous you will find some cafes, restaurants and small grocery stores open. Curtailed hours though.
In my visits I’ve stayed at Premier Inns, Club Quarters hotel, Airbnb’s and friend’s rental.
Alwaye made sure my accommodations had a refrigerator, a kettle and microwave. I’d buy what I could heat up (soups or chowders, pasta) bought on the day before. I always purchased my favorite Christmas sandwhich from Pret A Manger.
Also learned to love microwaving a pasta dish.
Loved the quiet on Christmas Day by enjoying long walks. Seeing families out and about with new coats, bikes, prams, etc,
Excellent time to explore London on foot so research a neighborhood with a public park.
IMHO the Queens walk on Thames River path is a great meander on Christmas Day.
EDIT 1: Regents Street, Oxford Street, Covent Garden, Kew Gardens have Christmas Lights. Tickets for Kew are a must.
EDIT 2: investigate what images will be shown on the Battersea Power Station ( now a massive shopping center ) . In 2024 it was Wallace and Gromit.
EDIT 3: Research Santa Runs. Rather charming to see people dressed in Santa Suits getting a pint following their running. Saw my first one in Victoria Park and recall grinning ear to ear. Total surprise, total joy.
EDIT 4: The massive Winter Wonderland will open in Hyde Park.
EDIT: See a Christmas Panto