We only caught a quick glimpse of the hospital exterior - I'd need to see it again and probably pause to place it properly. The interior hospital scenes would have been filmed at the Cardiff Royal Infirmary - possibly a few in the tunnels up at the Heath, but mostly at the CRI because it is closed and therefore fully available for use as a set. The red building wasn't the frontage for the CRI, though - might have been a side angle (it's a huge sprawling building), or poss one of the smaller hospitals in the Vale like Llandough. I'd need to get a proper look though.

Annie taking Mitchell out for a walk from their house in Barry all the way to the Cardiff Bay barrage was highly amusing...