If your 21.7mm that kit won't fit and will give play in the a.r.b as it wont clamp it tight.
Febi do a correct sized kit like you listed (For PR number: 0BF Stabiliser Diameter: 21,7 fitting side rear axle both sides - inside diameter 1 17 - inside diameter 2 19)
I sell those for £24.26 (febi pro kit) free p&p (I deal with lots of febi parts but even that one is not listed on my website, I can guess finding them wasn't easy!)
oh my website is
http://oemandmore.co.uk/golf-mk5-1k-136-c.asp if you need anything else (or message me on here if you can't find what you need)