Event space with outdoors in Central London

I’m looking for a space for a summer drinks event for our clients on 19th July, I’d really like a stylish pub/bar in central London (zone 1) with an outdoor space (but indoor as well in case of an English summer) - does anyone have any recommendations of any spaces without an astronomical minimum spend?

Tatteshall Castle might be worth a look

South Place Hotel in Moorgate has a great roof terrace