Upvote:3
The Excess Baggage Company offer left luggage services at all the major London termini and at the airports. Prices start at around £7.50 for one item for a few hours. You can get a quote online and book space ahead.
Disclaimer: this is just one company found on a Google search. There may be others. I'm making no recommendations.
Upvote:4
St Pancras station offers luggage storage.
Taken from Network Rail:
Left luggage
You can leave luggage at Excess Baggage Co in The Circle.
Monday to Saturday 6:00 – 22:00
Sunday 7:00 – 22:00
For more information call 020 8090 9923 or visit Excess Baggage.
You could also walk across the street to Kings Cross station and use their luggage facilities.
Upvote:4
The excess baggage company is 'very' expensive. And you can expect to pay £20 and up per item for overnight storage.
Another option is a company like stasher.com or bagbnb who broker storage at local hotels and business. They both have a couple of location just outside the station. I have used stasher once, and paid £4 for 18 hours. I was a bit nervous tbh. But all was ok and I used a small hotel just opposite kings cross. I did not leave anything valuable. Just clothing.
Not endorsing either service as I haven't used them enough to form a valid opinion.