Pros
Depending on your luck - you can get good exposure. Not having too many processes means you learn how to figure things out - which can be good or bad depending on your own style. Technology exposure is good as BT being main client tries every technology on the earth possible evey year.
Cons
Highly incompetent middle level management - the issue is for a technology solution provider -the bulk of middle management (now senior management) is very non-technical and focuses on people and politics - you wont see too many seniors taking interest in whats happening with client and how they can provide better solutions. This breeds sycophancy and manipulative politics - especially if you are very passionate and competent. If you are average - then things will be fine.