Changing flight times and limited time to transit at Singapore (from UK to NZ)

I'm booked on a flight from Heathrow to NZ via Singapore.
 The original transfer time was 2 hours, but has since reduced to 90 minutes.
 Will this be enough?
The UK to Singapore leg is using Singapore Airlines (run by air new Zealand) and the Singapore to nz leg by air nz.
I'm assuming baggage transfer will be automatic, but am concerned about having time to move from terminal 0(?) to terminal 3