The saloon skirt won't fit as the bumpers are different, but as long as the IS-C hasn't been facelifted then that skirt in your link will fit won't it? Or is it not available in the UK?
The F-Sport alloys are 19", but I'm not sure these bits are directly available in the UK. I think they're talking about the alloys off the IS250 F-Sport which are 18".
F-Sport 1
F-Sport 2