I have just finished this so can read the whole thread (didn't want any spoilers!)
I enjoyed it, but I really agree that if you can't think too hard about it. Round about episode three, I forgot what they were doing/their goal/who they were meant to be chasing/ the plot etc. So I just enjoyed it for what it was. Mainly London at Christmas. (Except strangely devoid of people!)
I think bigging up the baddies (The Clarks) and then featuring them in parenthesis, so to speak, just to get a cameo from Tracy Ullman (who was v enjoyable, tbf) is a bit of a cheat.
Also, Kiera/Helen had that interview which highlighted her translation skills as the reason she was hired. And then proceeded to do no translation whatsoever. I would have liked a cleverer spy/language/code kind of vibe, rather than so much killing.
Plus, I would have liked to know her cover job. There is only so many times she can go 'shopping' to justify a full-time Nanny, not to mention the night work.
A simple 'how was the office' 'oh, you know what Marketing is like,' or some such, would have sufficed.
I usually like Ben Wishaw, but I didn't enjoy him in this. He was too pouty and the just drinking prosecco thing irritated me. It felt like the info on this part of his story had been cut from the script.
Helen and Wallace's house is in Crystal Palace, apparently (the exterior anyway)