Hi Greg
I've often wondered about trying a set on my spare 17"s (especially after last winter!) but didn't bother in the end (mainly cost). Had a quick look online and found these:
http://ssl.delti.com/cgi-bin/rshop.p...110&sowigan=Wi
Not that many brands seem to come in 225/40/18s for some reason
and those that do seem to be expensive (£100+ per corner) but those seem a bargain. Although i've no idea how good they are as a brand.....