Where can we leave bags for the day around Tower Bridge?

[Train567]

Just that, we're getting the train from King's Cross later this afternoon bit spending the day around Tower Brisge. Don't really have time to detour to King's Cross to leave our bags, we're coming from the opposite direction.
Google brings up lots of suggestions of luggage storage like LuggageHero but lots of them seem a bit random, I'm a bit nervous of them.
There's just me and 3 kids so something straightforward and easy to get to.
Any suggestions much appreciated, thank you

We’ve used stasher.com very effectively in London.

I used Stasher, left my bags in a premier inn one time and the storeroom of a restaurant the next. It’s honestly fine. Bet they have lots of places round there.

2 recommendations for Stasher, I've booked a Premier Inn one nearby. Thank you.
I'd never heard I'd this sort of thing before so I wasn't sure, the first few I clicked in looked like they were random corner shops. Not that our bags are full of anything valuable anyway, 47 stuffed toys and some dirty clothes