Thanks for all your replies much appreciated....would i be able to purchase a selection of different paintballs in trial size packs to see which would be more suited for any particular marker?
I doubt it but whenever you get some paint, try it. Put one in one end of the barrel, and blow through it. If it rolls out without blowing, the paint is too small, if when you blow it doesn't go through, the paint is too big. But, if when you put the paint in it maybe rolls for a bit, stops somewhere and then you blow it and it comes out easily, then you've got the perfect paint.
Just note down what paint it is and the rough temperature and so you will know whether or not to buy that paint again.
Shimples