Spare Wheel for W219 CLS

[siremastimus]

Hi, just got first Mercedes a 2010 Grand CLS and love it already. Just noticed though there is a big hole where the spare wheel should be!

Would this be OK for a W219 CLS?

Mercedes ML Spacesaver Wheel & Tyre 155/90R18 Dunlop Reduced From £99.95 | eBay

The car has 18" alloys at moment but notice a lot of spares for the CLS are 17" so not sure what size I need either?

Thanks all