Thanks for the advice Clive. Not sure I really follow your comments about 12mm minimum size available, The tyre fitters suggested hub centric spacers, and I've seen these for sale with 5mm and 9.5mm thickness.
The wheels are Zender Siena's and the mounting surface that the bolts pass through appears to be quite thin, compared to the standard teledials.
The wheel size is 18 x 8 with 225 x 40 x 18 tyres.
stud pattern is 5 x 98 as you would expect and an et28 offset.
I want to be sure I get this right, as it was rather embarrassing having to retreat from the tyre fitters with my tail between my legs!!
2015 - Today 159 2.4 JTDm
2012 - Today GTV 3.0 V6 24v
Gone by not forgotten!
2013 - 2015 156 SW 2.4 JTD
2013 - 2013 145 QV Shed for 1 week - RIP
2011 - 2012 Brera S 3.2 V6 number 21/178
2007 - 2011 GTV 3.0 V6 Q2