Renault Megane possible head gasket blown?

Hello people, just a question about my Renault Megane 1.6 16v petrol. I have noticed oil mixing with my coolant, leaving a brown creamy substance layering the top and cap of coolant. Also I have removed all my spark plugs and plugs 1&3 are oil fouled, on the tip and in the wells. And finally my lambda sensor is flagging up my engine warning light, I know this because I used an obd reader to check problem. I just wanted to ask peoples opinions on wether this is most likely the head gasket. I would think it is but I don't seem to have overheating or smoke in exhaust. Any input would be much appreciated.