Pros
Fairly good social scene in Crawley office, good work/life balance. The experience I had was that it didn't really matter whether you tried hard or not, your promotions are pretty much decided purely on how much time you've spent at the company and not whether you are any good at the job or not. (2 years for Project, 4/5 years for Senior). This is good if you just want a steady job where you can breeze through each day.
Cons
Senior management for group I was in was absolutely abysmal (too busy managing upwards), no career prospects whatsoever. In all honesty, I could have put in half as much effort as I did and would still have achieved the same career path. There is a lack of openness from the highest level downwards which often leads to a rampant rumour mill.