I've swapped it with a tmc v2 skim 600. The internet shop that I bought it from were kind enough to take it back even though I explained the problem was with me not the equipment and it was now used. I'll be using them as much as I can in the future.
It said to let it settle down for about 48 hours, not with the water level at full skimming height, therefore the amount of air is only going to increase. However, the guy from aqua-medic said that some salts have an agent to help skimming and that this may cause "over-bubbling" but he seemed to think it would settle down eventually. I'll keep you posted, thanks for the advice as I would have been completely tearing my hair out otherwise. I think I will ignore it for a few days and then see if it has improved. Did yours produce alot of bubbles at first, or did you put it on a mature tank?