2015 Volvo XC60 coolant loss

My XC 60 (15 reg) is losing coolant at an alarming rate. It has been into the Volvo main dealer 3 times and has had a cold and a hot pressure test with nothing found. They are now talking about gasket or engine block problems costing £1200 - £5k to fix . The car has only done 66K miles and it is a Volvo which I thought were bombproof. Does anyone have any idea as to what the problem may be and hoe it can be fixed for less than these huge costs?

It doesn’t sound like they have diagnosed the problem. I would not start an expensive repair on such a vague statement. Exactly what is the rate that you are losing coolant?