police genre (not spy, but good intrigue) you can try some of the Masterpiece Mystery shows on Britbox or Acorn TV. My favorites have been Endeavour and Shetland but there are a ton more. Luther is great too. I just started the second season of Guilt and am enjoying it too.

Because British TV dramas aren't forced into the 60-minute format (which, with commercials, leaves you only 42-44 minutes of content) the episodes are often nearly twice as long as US dramas, meaning you get a lot more character and plot development and things are less predictable.