Its what the forums for lol ask as many questions as you want. Unless its obvious things a search would solve.
Doubt the arb would have anything to do with the camber some of the early 106's didnt even have an ARB at the rear!
Is the camber on just one wheel? /----|? Tyre wear uneven? Does the car feel like its being taken by the wind and as though the rear end steps out?
Most likley is the beam mate. Fix the arb end plate as either way refurbing the axle or not you will need a new plate, see how its goes if it dosent solve things get a refurbed beam. Second hand beams can be fucked and you will only realise once its fitted to the car, orr it could collapse a few weeks later. Yorkie on here fitted something like 6 all of which were useless! then Settled for a refurb.