This is the first car I've ever bought on finance, I've always saved and paid cash.
Every single way I've looked at it, I can't find a reason why this particular PCP isn't the best way of buying a new 200. They depreciate like a rotting peach and because so many get sold on PCPs you're always competing with dealers giving them away. Meaning unless you have cash, a 2 year old car can be more expensive to buy than a new one, so why would someone buy your used one?.. look at the trouble people are having shifting 197s and the hit they've taken.
Ignore what it costs and what it's worth, you're just paying the depreciation @ 4.9%, with the GFV offset costing you nothing, that's all.
If you loaned the money, and sold in 2 years time, you'd have lost the depreciation and the extra you've paid on a loan for the full amount @10%.
People also seem to think you're locked into the deal too, you can give the car back at any time, you'll just lose the deposit and a month's payment. If you can't afford a loan any more, you've got to sell the car and pay it off, then you're in the realms of negative equity.