You shouldn't need spacers if you get your wheel size and offset etc correct.
I'm running 9" wide BBS's on the rear, they don't rub and have a decent amount of poke.
My wheels don't have adaptors, spacers or even spiggot rings (bolt straight on FTW).
However if you're buying BBS's they were only dealer fit and seem to have been discontinued for some years now (mine say made in WEST GERMANY on them) so you have to buy whats out there and they're not all any use for Saxo's.
Good luck with it all, will keep my eyes peeled for updates