Hi Rob,
Sorry to hear about all your troubles. It's situations like this that that highlight how far Caterham have to go to restore customer confidence (take heed Mr Lashley).
For such a young car to show this level of corrosion, it make me wonder where, and how, it was stored during it's short life. I have seen cars that live near the coast to show atypical decay, however, in this case it may simply be neglect......not from you, obviously
All the previous advice is sound and I sincerely hope this experience has not put you off Seven ownership.