The fact of being geographically flexible in the UK could be a problem sometimes, depending on which is your situation.
The salary is not quite a lot, but most of the employees are recent graduates, so we can not expect too much.
If you break the contract before 2 years, you have to pay to FDM the training fees, which are £20.000 Despite the fact the training was really good, I think that's too much for just some weeks. I would say that's the only important con of FDM.