Pros
Outstanding variety of work, the local team in the Madrid office are fantastic people. New Madrid office on Gran Vía is really nice too. Madrid pay is excellent relative to Spanish salaries, and the regional UK offices pay decently as well.
Cons
Working with the technical team leads in London is a truly disgusting experience. You can never trust a word they say, even if it's in writing half the time, and they will chew you up and spit you out. I was lied to my face repeatedly by higher-ups. Micro-management is also through the roof with them; you find yourself questioning even the phrasing of simple Teams messages. They persistently play politics with people on lower grades, openly devalue you in front of colleagues, and are hilariously clear about playing favourites. People at lower grades should not have to have stand-up arguments with someone in a leadership position of another office (London) when the latter tries to blame an intern / graduate for something that one of the London team messed up.