Whats wrong with my landrover freelander.?

I have 1.8 Freelander & within 3weeks it broke down,i was towed to the garage & told that the water pump had failed. �400 later it was fixed(plus new cam belt).But it continued to loose water,there was a gushing sound from behind the dash but no leeks that i could see or oil or water anywhere it shouldn't be.It went back to the garage & they told me that they thought the head gasket was about to blow so advised me to get rid!I didn't want to have to do that so i took it back to the garage i got it from -he had it for 2weeks & told me that their was nothing wrong & it hadn't lost any water in the time he had it. I took it home & within the next 70 miles i did in it ,it took a total of 7 litres.I drove it back to the garage i got it from furious,again 2weeks later he ures me that he has now replaced the head gasket & all relevent parts that entails. But as i drove it home i was sure that i heard the water gush slightly behind the dash again..HELP!! (the floor is not wet in the front)