Spigot rings are fairly cheap. I got mine shipped from the states as I was browsing ebay, but I think Kingdom alloys sell them for about 16 quid.

As FunkySee said, 215/45 or 40/17. The rear isnt going to be an issue at all, even on standard arches I have plenty of room with 225s and could possibly go wider, it's the low offset on the front that will screw you.
215s on an 8 will tuck the shoulder of the tyre in a slight bit and some camber in the front will sort out the rest