When I picked up mine I had them put the skinny + jack kit in. 190 Euros inc taxes.
My understanding was that a full sized 18" wheel will not fit in the well.
But the kit comes with 2 retaining bolts: One for skinny and a longer one for a full sized.
Maybe the best thing to do would be to take one of your 18s off and see if it fits.
Maybe it's only that it doesn't sit flush?
If you want a laugh about such design issues check out what JLR did to accommodate a full-size spare in the F-Pace:
http://www.fpaceforum.com/forum/attachment.php?attachmentid=9305&d=1466014295
Worst.
Solution.
Ever.
My understanding was that a full sized 18" wheel will not fit in the well.
But the kit comes with 2 retaining bolts: One for skinny and a longer one for a full sized.
Maybe the best thing to do would be to take one of your 18s off and see if it fits.
Maybe it's only that it doesn't sit flush?
If you want a laugh about such design issues check out what JLR did to accommodate a full-size spare in the F-Pace:
http://www.fpaceforum.com/forum/attachment.php?attachmentid=9305&d=1466014295
Worst.
Solution.
Ever.