spot on Nick, most of these conversions are half hearted, be prepared to actually LENGTHEN the suspension geometry (Bloody difficult on a macphearson strut system, but very possible.)
Spacers from the hub outwards are ok for about 10-15 mm at most, after that you WILL be asking for trouble - the same applies to wheel ofsets too.
you will need to space the complete hub(s) outwards to do it correctly.