I am just about to fit the gear cable to the gearbox/paddle shift.

The only cars I have seen to date have the cable on the left hand side of the paddles sweeping round to the left hand side of the scuttle and then back on itself to the gear shift

I may be wrong, but does that mean if you pull back on the right hand paddle then you go down the box rather than up. Is this the case or do I have it all wrong and can it go either side

It doesn't matter which side as long as you know which way.
Don't forget that it will not be all one direction for up and down.
From Neutral the shift lever has to go forward into 1 and then back for 2-6.

Most i have seen are on the right going to the gear lever at a 6 o clock position - i posted pic on this in bec section if its of interest.
Adam