Last month, I flew LGW-IST-TLV in C as a *G. I even called the USA office for Turkish and could not get a clear answer as to the allowance for gold in C.

When I checked it at LGW, my checked luggage totalled 41 kg. The agent who was a contract worker had to call the supervisor to ask for the rule. I was cleared and the amount of 40 kg was printed on my boarding pass.

The website said I would be permitted 1 carry-on of 8 kg. I carried 2 both over 8 kg. I noticed that there wasn't a check on weight of carry-on as long as it wasn't a giant piece of luggage. You may want to put a few kg in that carry bag rather than paying an excessive weight charge.