Pros

You will have the opportunity to work with cutting edge tech. If this is important make sure you state this as a requirement when you apply, because this varies a lot depending on which team you go into. I have found line managers are very supportive. It is easy to switch teams if your experience is different. I have not encountered anyone with problematic people skills. The recruitment process filters them out well. Pay is good for Hertfordshire. If you live in London and plan to for the foreseeable future, you can do better.

Cons

Lack of parking and poor public transport connections. Working at home is rarely an option. Unless you live within cycling or walking distance of the office, your commute will be stressful. Management are penny-pinching in some areas (e.g. software licenses), but wasteful in others (e.g. unnecessary town halls that tie everyone up for hours). The main office (Trident Place) has poor facilities. Be sure to keep a portable fan and warm jacket at the office to be prepared for 15-27C temperatures. Throughout 2018, overcrowding was a problem. Sometimes, you may be queueing 30 minutes for sub-par canteen food. Maybe it depends on which team you are in, but I have not found the work very challenging or my time well-used. Feature development seems very slow. Mostly due to lack of motivation/incentives, indecisive business/retail and poor processes. Backwards security policies - inconvenience when it is not needed and disregard for the real risks.