I have had another look today and it is engine oil. The breather hoses on the engine where pre-installed and I've connected up the catch can and looking in that area i can't see any leakage around the hoses, but its all pretty tight in that area of the engine bay. As the Sigma engines are pre-filled with oil, I just checked the level, and it's up to the max so I've not added any additional oil. I did get a reply back from Caterham this morning, saying they would address it at the PBC, shame if they have to undo all the work I've done. I may fire her up again to see if I can spot anything I'm based just south of Edinburgh