Pros
Very accommodating for all types of flexible working patterns including start/end time, working pattern (e.g. MTTF), half day Fridays. For example I generally work 7-4. Over time is paid at 1.25x rate. Plenty of opportunities for progression if you are driven and willing to take opportunities that are presented. Friendly work environment, with a very "flat" feeling structure and the ability to challenge or raise concerns and questions with anyone. Large company with many projects, hence always meaningful and challenging work to be found. Decent benefits, including 14% pension contributions (personal contribution 6% and company 8%). Can make a large impact in a short period of time, with responsibility quickly earned and expanded.
Cons
Some of the benefits could be improved, such as maternity/paternity cover, private health care providers and the share scheme. Some processes can feel slow, and making change in a large company can time. This has definitely improved in recent years.