Can anyone advise me before I get ripped off by garage. My multipla (3 & 1/2yrs old, only done 18,000 miles) Had service & mot end November, running fine before service. Came back saying needed coolant top up, otherwise passed Mot, no big bill. Within a week light came on to say 'temperature high, engine cool'. Immediately got coolant & topped up with coolant & water mixture as per instructions. Seemed ok for week or so then light came on again. Heaters not working & fan running on a minute after stopping car. Didn't drive it over xmas, light came on again today after first outing. Discovered coolant all gone! Checked oil, no milky deposit on cap, but milky on dipstick. Is it my head gasket (help, pricey?), or maybe just leak from coolant? Any advice most welcome. Booked in local garage for Thurs, not dealership where it was serviced, suspicious they might have caused coolant leak in first place!