I had the factory molded mud flaps installed at delivery back in nov 2011. However later during the 2011/2012 winter one of the rear one got ripped off while backing up in my driveway in fresh snow. NOT icy packed snow.
Those were held in place with 1 screw each and 3 push pin type of things. the rear bumper does not seems to allow for a firm fit and hold, at least on the Sedan, anyways.
So since you are in London and get the same kind of winter conditions we get, I say gor for it as they look good, but be extra carefull 'cause they are very easy to break.
2012 Oxford White SEL Sedan
303A + winter package + Moonroof + 16'' OEM