Thanks Mart. Yes we suspected that might be the case and Eli confirmed it when he wrote back saying the 8" wheels were actually 9" and the 9.5" are 10.5".
We worked out my frontspace using a wheel of known offset with tyre fitted, allowing for tyre bulge to clear the wheel arch. But it would be great if you could send me that diagram please - helps put the mind at ease!
samps8@hotmail.com
Thanks