Astra: Condensation or head gasket failure?

[buckaroo2]

An elderly relative has an Astra 1.6 '00 with average miles. He only does about 10 miles a week (start-stop shopping trips) and has done about 250 miles since having the car (from a garage). I recently checked the oil/fluid levels and noticed that there was a creamy emulsion on the inside of the oil filler cap (light cream in colour which, when wiped off, returned after a journey of 5 miles or so). The dipstick oil is clear and the water level doesn't appear to have gone down, nor is there any oil visible in the expansion tank.
How likely is it there this is condensation rather than a head gasket failure (or could it be another gasket failure?)? Apart from taking the car for a long drive in a bid to see any change in the emulsion is there a simple and inexpensive way to check if there's something awry?
Thanks
A similar question was posted a while back and those replies noted. How long would it take for the excess condensation to be removed from the oil, if this is the cause, in terms of journet time (excuse the clumsy wording of that sentence).

[Toureman]

It is condensation not the head gasket.

Blank off a third of the radiator to warm the engine up, that might cure it, the Astra engines are over cooled.

[ianess]

I agree entirely with Toureman about Astras being overcooled. Mine has run a lot better since blanking off part of the radiator as advised in a previous answer.

[wacky racer]

My wife's car does exactly the same thing - 4 to 6 miles a day. It's not good for the oil and therefore not good for the engine. Once a month when I have a motorway journey to do I use her car - it helps a bit. The only other solution is to change the oil (and filter) more frequently.