I bought my little W reg a week ago for £500. Expensive you might think but it only has 119000 on the clock, full service history and loads of bills including ones for cambelt and water pump replacement May 2011, no rust and generally a tidy car. Anyway my coolant light came on the other day, I was in the middle of nowhere so had to drive around 10 miles to get back to civilisation. A kind gentleman looked at the engine and said the head gasket had gone. This was the first time the coolant light had come on and there had been no other indications that the engine was over heating. Several questions:

a) Would the head gasket not have been changed when the cambelt was?

b) If so, is it normal to only last 18 months?

c) Would I have done serious damage driving the 10 miles after coolant light came on?

d) Any rough ideas as to how much it will cost to repair?

I might add that it was a private sale from an elderly gentleman who seemed genuine but would I have any recourse to the garage that replaced the cam belt?