Could this be a blown head gasket?

Hi All i need a bit of help, ive always been taught when a head gasket goes there would be a mayonnaise substance in the water tank or on the oil cap but mine dosent have any. Ive just done a 400 mile round trip and shes emptied the water tank twice, shes running like a bag of bolts on idle and man is she drinking alot of petrol now but i guess that's due to the fact shes trying to compensate for the erratic idle. I don't have massive amounts of white smoke but i did see some when i was stuck in traffic on the way home today. I also have a whistling nose from the back middle towards the right near the battery and i think that's a vacuum hose but i am going to look for that later i don't think that could be a symptom of a head gasket. I was wondering if this could be the head gasket as i am not looking forward to stripping the engine down:S I have a 1995 LX Ford Escort 16v 1.6 EFI engine. Thanks for your help all:).

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