I'm assuming its like a heat shrunk type fitting from new, as you say there are no clips on it.

Has the fuel been altered in NZ?

You've probably seen that here in the UK its got a higher ethanol rating (E10) now and its eating older fuel lines and in some cases new hoses aren't lasting very long as its eroding the linings.

I'll be getting some Gates Barricade when I get around to changing it.

Personally Ive always used super unleaded in the Sierra.