Thank you for the advice guys,
I may be wrong in my assumption then, as I don't have any overheating issues, quite the reverse, I think the thermostat has stuck open, as it takes ages to warm up. However what made me think it was a head gasket problem was finding a beige coloured creamy substance inside the oil filler cap and also the same round the top of the dipstick, which I know is a result of oil and water mixing, and I thought the gasket may have gone between the oil and water galleries. The old girl has done 220 k miles, no rust, and in 4 years of ownership has cost me £120.00 in repairs, £50.00 being a battery plus the fact, my 6 year old daughter loves the car, and would never forgive me, so getting rid isn't really an option.
Once again any advice would be a great help, and much appreciated.
Iain