Right ive already posted this twice already so here goes a third...
Get these spacers instead - use your original bolts and locking nuts! Theyre much safer than getting stupidly long bolts also:
http://cgi.ebay.co.uk/20MM-Hubcentr...yZ122154QQrdZ1QQssPageNameZWD1VQQcmdZViewItem
BTW i am in no way affiliated to this ebay seller, although i should be on a comission at this rate!
I bought some of these 20mm spacers at the weekend from AC services. Orginally bought some 15mm ones but couldnt get them to fit as the spigot was too long for the spacer to fit over. Defintely go for the 20mms. They are really good quality, hubcentric and very cheap at £34.50. bolts included.