hi, thanks for the replies.
Its been losing oil for a while. Not major amounts just generally needed topping up every now and then.
The problem has really got worse in the last week or so. using litres of oil, had to add almost 5 litres in the last week, covering about 150 miles in the process.
There's no oil physically leaking, and there is some in the water but certainly not 4 litres of it. In fact the water level is slowly falling.
The car is also down on power.
Am I just talking myself into head gasket??