There's no mention of an LPG 207 Gti on the Peugeot France website.... The model lineup looks the same as in the UK.
IMO your giving your dealer a get out of jail free card if the car has any engine related problems. I'd only go for it if you can return the car to stock without any sign of the installation being done, which is probably unlikely.
Have you considered a Dooper?
Sorry to sound negative but I don't see the point of getting an S for learner car, if I had learnt to drive in one I'd have been gutted when I passed my test cos I wouldn't have been able to afford one for myself or the insurance! It'd be awful moving from a Cooper S to say a 1 litre Corsa.....
Then there's the boy racers and old grannies learning to drive in something that does 0-60 in 7 seconds...