Guaranteed future value - it's the balloon payment at the end. It's guaranteed in the sense that it will never be any higher (or lower) regardless of the cars value. You can normally ask for it to be lowered so your payments and therefore equity are higher.
Yes, at the end of the term you have 3 options
1 - hand the car back and walk away. Subject to fair wear and tear and this is the only option where the excess mileage costs come into play
2 - pay the GFV and keep the car (this should be lower than the actual value of the car)
3 - trade it in and use the difference between the GFV as a deposit. Like I mentioned earlier, you could also sell it and pocket the difference, but takes a bit of coordination.
So in answer to the question about if you have nothing to show, or if there's equity, or if you have to stump up to keep it.... Yes is the answer
It basically is just a loan secured against the car, just structured with a balloon payment at the end so you end up just financing the depreciation. It makes it quite flexible but the interest rates are higher than a bank loan, which is the tradeoff against the convenience
Ah, so with the new STI. OP pays the £15K, pays £125 a month and has £17K at the end of the term "equity" in the car. I guess it doesn't sound "that" bad. Have to be honest, think I'd rather just buy a car outright for £15K and be done with it.