C70 Coolant Leak, cannot find its source?

Thank you for your reply Ken. No damp in the carpets and no gases in the cooling system. Took the car to the garage (shop) and left it with them for 10 days whilst I was on holiday. When I arrived at the garage, water was pouring from under the car so a relief that whatever was failing was now seriously failing so an easy diagnosis. Not so. About 15 mins after I left the mechanic topped up the expansion tank and put the car on the ramp. He couldn't get it to leak again! So the following day they drove it a few miles and popped it straight onto on the ramp when they got back. After a while looking he found a tiny split about a 1/8th inch/3mm long in the short hose (about 4 inches/100mm long) from the thermostat housing to the manifold. The hose is about 1/2 inch/13mm in diameter. Once replaced no more leaks. Presumably the split only opened up under certain conditions, maybe when the thermostat opened/closed or due to engine movement. Anyway, I would suggest that any hard to find leak on a Volvo C70/V70 etc could be that short piece of hose. Picked the car up on Monday, covered about 30 miles and so far no leaks! Will be checking coolant level next time I drive it.