|American shows do manage it though. I suppose their budget is bigger but why would that make it get done quicker?!|
They can afford larger ensemble casts and second and even third filming units, so lots of stuff can be filmed in parallel, same in Post Production. More cameras rolling can cut down repeating scenes for angles and coverage. Also for location work, many places in the US encourage use to promote tourism and have filming units to make it easier to get in, close off areas and get out also speeding things up. Many large filming complexes in US and Canada also have huge backlots again cutting down set up time. UK just doesn't have this scale of resources available.