Yep pretty similar, technically in the UK they can go up to 96hrs if the police just ask a judge for an extension, even without formal charges. So about twice as long as the US's theoretical upper limit.

My main concern is the fact they are raiding peoples houses, taking electronics, and aggressively interrogating people for hours over a tweet, then pushing them to sign a document admitting they did something wrong without charging them. While everyone pretends they just got a 'warning' and it's not a big deal that this happens to thousands of people a year.