How can I ficx my Firebird Boiler?

I have a firebird combi 70 boiler.

Today the water pressure started falling quickly and caused the boiler temp to rise too high and cut out. I refilled and noticed that the water was being lost through the condensate pipe. Does this mean that the heat exchanger is leaking?

While the boiler was running after refilling it locked out - would the leak cause this, or the rise in temperature? Or is this due to some other fault?

Mark
July 2010