VX Commodore doesn't start on first try, oil pump, leads, filters and plugs have been changed about a year ago.

TBH, it hard to say anything without having a look. The common issue could be a fuel pressure problem. It may not be retaining the pressure after you turn it off. When it is cranked the second time, it has been primed twice and builds up more pressure. Remove the vacuum hose from the fuel pressure regulator and see if you can smell petrol if so replace it.  Otherwise, we would recommend getting a professional look from a mechanic.