FinbarrG

hello, I have a Corsa 1.4 Petrol 2007. I have a few questions on it. The car is going fine except that it is using water not alot. The car is not over heating. When i checked the water bottle it was dirty with small creamy deposits in it. I checked the oil cap and there was alot of creamy brown deposits on cap and sitting below it at top of engine. My first thought was head gasket. When I spoke to a mechanic he said to check the oil cooler as they can gave trouble and gaskets go allowing water and oil to mix at that point. I took off the exhaust manifold tonite expecting to see an oil cooler to side of the oil filter housing , but there is none there. Can anyone tell me if there is one on this car and if so where is it. Or is there another test to see if it is the head gasket. I forgot to say alo that I removed the thermostat from the water pipes and tested that by dropping it into a jug of boiling water, there was no change to the stat. would that indicate that it is done also and needed to be replaced. I have attached a sample of the creamy deposits left in one of the hoses and also view of the engine with exhaust removed where I would exspect to see the oil cooler, the oil filter housing is just in view on right side bolted to block. Alot of questions, but any help would be great.