Received a complete set of new bushes for the roadster today, the seller told.me that in the Haynes manual the bore size is incorrect at 12.5 and should be 12.1 to 12.2 so now my original m12 bolts won't fit the new crush tubes so my question is what is the best size to get to fit the tube?

M12 bolts should pass through a 12.1mm hole, after all they are slightly less than 12mm (11,966 - 11,701mm)

The seller is correct in that ideally they need to be tighter than the Haynes (although there must be a fair few cars out there with Haynes spec crush tubes and no issues!), but your M12 bolts should still fit. The next size down (M10) will be far too loose.

Exactly my thoughts that the bolt should go through, but as soon as the thread gets to the hole it won't go any further, the original bolt is the same, I'm thinking that maybe they haven't been drilled correctly.

first have you checked the actual size of the bolts your using ?
(just to make sure they are M12 not ½" )

you really need vernier or digital calipers to check these sizes
like these:
http://www.machinemart.co.uk/shop/product/details/cm145-digital-vernier-caliper?da=1&TC=SRC-caliper



[Edited on 11/7/2014 by mcerd1]

What mcerd1 said. ^^^^

You've more than likely got 1/2" UNF bolts which will measure, um..... 1/2".

Now having some experience of these 12.1mm crush tubes. Some measure at above and some below 12mm so 12mm bolts will not fit. The sizes I had - maybe a different supplier, maybe not , were all over the place on sizes from 11.7 to 12.4 mm :-(