Right I think I know the answer to this, but just wanted to check with those more knowledgeable than myself!        Im pretty sure the Caster is uneven on my Octy MK1 VRS, theres a measureable difference between the rear of the tyre and the sill when comparing both sides, its also noticeably harder steering one direction than the other.  

 

From what Ive read the caster is not adjustable on the MK1 Octy without fitting caster adjustable bushes/arms - or can it be altered by other means?      If it isn't changeable then the logical conclusion would be that some part of my suspension is damaged in some way (most likely an wishbone im guessing) as thats the only real way it could be noticeably different?    

I would check your wishbone bushes, as in standard form, there is no adjustment for caster on the mk1 system. You will be looking at Superpro bushes or the like to do this if it is not wear and tear.