With a decent sealant on the paint you can just pop into a jet wash and stick £1 in the machine and rinse off anything it's picked up. I find I usually do this mid-week to keep it looking clean (Sat/Sun is wash day).
Limestone grey is definitely a nice colour and not one that is seen very often so you'd have the unique feel to it but the GTI/D exclusivity of Carbon Steel Grey makes it a better choice IMO.
Plus it's one of those colours that surprises you in different lights. People think it's black, grey, green, blue..
