XKR MY 2000

A couple of months ago the coolant low light came on and I have been regularly topping with water. At the same time at start up each morning the car runs rough for a minute, then seems OK.

Took it to the workshop and had several hoses replaced as they were leaking, however coolant light came on about a week later. Took the car back and they replaced one more hose. However I also explained about the poor running at start up.Workshop indicated that I could have a head gasket leaking issue and the poor running is coolant in the top of a piston or 2. There is no water in the oil the last time I looked.What do I do. I havent had anything else checked ( spark pluds fuel injectors etc) but the car has only done 80,000 and has been serviced every year. Should I just wait and see or if it isnt fixed now it can get worse and do even more damage. I am in Sydney, Australia and have been quoted at least $8,000 to remove head, get it machined etc and replace new gasket. Can anyone recommend a good mechanic to better diagnose the likely issue

Cheers