Per previous thread http://forum.vectra-c.com/showthread.php?t=58878
What can I say I purchased some second hand 4 x Sport Contact 2's 235/45/18 a couple of weeks ago and so far the tyres have been excellent. Very low road noise, no tram-lining and excellent grip in the dry and wet. The tyres had only a very small amount of wear on them and cost £40 each fitted!
Other plus points:
They fill the arches more and look great with my BK999's 18 x 8J's, I suppose I had better post some pics up
My speedo reads correct in that it matches my satnav speed as well
So the outcome is I would recommend Continental Sport Contacts 2's for the Vectra C