Yep - so I checked the wheelfitment.eu site, which gave me tyre/wheel options for the Panda 169, and they range from bog standard 155/80 x 13 up to 195/60 x 16!
Possibly the 16" is for the 4x4, but they don't specify that.
Thanks for the various helps, guys. Think I'll chicken out and go for 15"s with winter rubber.
Since we'll have both shelled out £200+ on winter tyres, a warm, mild winter is almost guaranteed.