I have a Citreon c5 2.2 with a citreon towing ball which has a plastic covering over the ball (not the ball dust cover),should I remove this covering off the ball,the hitch on the caravan is a friction type which clamps to the ball
With the plastic cover, the ball will surely be larger than the standard 50mm +0mm/-0.39mm so you shouldn't even be able to get the coupling on regardless of whether you have an integrated stabiliser or not.
It really would surprise me if a towball with a plastic cover would meet durability requirements. If you have an integrated stabiliser it certainly won't. I therefore assumed that the plastic cover was only there for corrosion protection until first use. Without having a closer look at the hitch it's very difficult to make any further comments.