I was going to mention about buying a mini cooper s woks and tuning it up if your worried about the seats? also my mates mrs has the coopers S, had it for around 3 months now and loves it but just doesn't like the fuel bill! around here the BEST she can get is 27mpg! I don;t know what other people get but I thought thats terrible for what power they are.
.......At the end of the day its up to you! - just remember the other running cost's mate, tyres etc...18in iirc?
On a long motorway journey you get at least 32, although around the city i do get 22