sorry me again
the book says that the rear shox must be square/ vertical to the upper mounting point, if the axle is mounted about an inch or so further back in the chassis would this alter handling or cause other problems, martin

No.

No

"sorry me again"

Don't appologise, I double checked just about everything I did on here to make sure I wasn't about to cock something up

Short answer: No

Longer answer, off by 1" over, say, 12" is an angle of about 4.5 deg. All that means is the shock will move 0.4% less then it would if directly above. You'll never notice.

I had to move my shock about 75mm back from the center of the diff, because my shocks are too long.
What influence will this have? I have standard 180 lb/inch springs.

You'll be fine.