Is someone trying to out-pedant me?    

^ ^  does 1/2" make all that much difference? (bobdog lives!!)  

900000 calls 215/60 'marshmallows'.  Not that many years ago when 65 or 70 section was par for the course, albeit on narrower width (185, say).  Simplest thing if you want to press on a bit is to put a few more psi in the tyres, especially in cold weather;  then they never go below the recommended pressures.  We've ordered an S (1.2 manual) to avoid 17 inch wheels and drug-dealer windows;  improved FL spec made this acceptable - although options list is pathetic.  The other factor is that the 16 inch tyres are H speed rating (130 mph) whereas 17 inch tyres are W speed rating (168 mph - for a 1.2??!!)  Achieving the speed rating must necessitate design compromises in wear and comfort;  so they wear faster and cost more to replace.  Example:  Michelin Primacy HP, Blackcircles.com:  215/60 16H:  £124.62;  225/50 17W: £164.21.  H is a bit cheaper in 17 inch, but will upset your insurers (or rather they'll upset you by refusing a claim).  Stupid, isn't it?  I suffered 17 inch 50 section tyres on a Mazda 5 for 18 months, and wouldn't repeat the experience.