Pros
FDM have an excellent range of clients which will usually secure a good salary and full-time employment with the client after 2 years of employment with FDM.
Cons
The training, while adequate, can be achieved online for around £500 and far less than the £20000 cost and two-year commitment that FDM ask for. FDM will pay you a sub-market-value salary throughout the two years that you are employed by them, else you will have to pay the £20000 training fee. Working at FDM has few (though growing) benefits, including limited holiday time, no further training or input into personal development. If you can reasonably get a graduate IT job in any other company, including FDM's clients, there is no good reason to apply to FDM (though it may be an acceptable last resort).