2000 Vauxhall Corsa Head Gasket

Engine Mechanical problem
2000 Vauxhall Corsa 6 cyl Automatic

Hi,

Just need some advice please. I've got a vauxhall Corsa 1.2 got it 6 months ago and everything seemed fine up until now. I noticed a while ago that my temperature gauge was going off the scale and on this occassion had to call out the RAC who could'nt see a problem with it and suggested it could be the fan and asked me to take it to a garage to be checked I took it to a guy who I know who is a mechanic and they said it was fine. Anyway used the car more noticed I was losing water and the temperature gauge was again going off the scale. Asked my Friend again to have a look at it which he did briefly asked me to take it to him the following day he noticed a puddle off water underneath my car once my car had parked he checked it and following day changed the Radiator. On checking it he said there could be a problem with the head gasket and said one of my cylinders had gone.
Told me to get my head Gasket done which will cost me under £500 if he does it. My Friends are not convinced this is the problem as there is no white smoke coming out of the exhaust and the oil seems ok and is not mixing with water the only problem I am having is I am losing water rapidly and I am topping it up daily. Temperature on the gauge seems to be fine at the moment

If you could give me some advice what the problem could be I would be grateful as I keep getting told different things and I am now not sure

Many thanks