condensate is perfectly normal when cold started and till engine warms up, Its stuck in exhaust
The water being pushed up from radiator cap neck while allowing warm up is also normal - the water is expanding due to temperature.
The oily film maybe from engine assembly or if grease/oil was used on hosepipe nipple barbs. (how thick is this film?) - if its just in reservoir, remove the reservoir, siphon out the clean coolant from below the oil line, then wash the reservoir bottle out with detergent to remove the oils, reinstall and refill the clean coolant you collected.