Pros
Most teams support flexible working arrangements, there's lots of training provided to employees and they hire very good and friendly people. The people you work with on a day to day basis will be great. Benefits are good if you have a family.
Cons
Promotions are difficult as the upper management tend to stay on in the company and it's about who you know rather than rewarding the best people. Although they have a large finance presence in Sussex, the main movers and shakers are in London so you'll need to take a role there to really get on. The Corporate "family" values of the company don't seem to be embodied by the upper management and seem only to be there to keep the masses content. There is also constant restructuring - I've been through it each year I've worked there.