I know the Boeing 737NG manuals mix and matches the phrase "cargo fire" and "cargo smoke" throughout them. There is no heat/fire detection in the cargo holds (unless it's an option that I haven't come across) it's purely a smoke detection system, which can be "fooled" by anything that might reduce visibility across the sensors.
How does your company deal with fire/smoke indications? Always treat them as real?
If the ARFF have thermal imaging cameras they may be able to advise you whether or not they are picking up a heat signal.
In your scenario, I think I would be inclined to do as you say, taxi to an aerobridge with the firetrucks following behind. The other thought I have, would be to request/demand a pier that has good access for the ARFF. I note your location as Sydney, so I wouldn't want to end up down the bottom of a cul-de-sac, I would want an aerobridge either at the end of a pier, or if possible one with adjacent aerobridges clear. The ARFF/Sydney Airport owners/operators/your company may of course have other ideas, but an aerobridge at the front, steps at the back and a precautionary disembarkation would be something I would consider.
And of course make sure the ARFF don't open any holds/E&E bays until all the passengers and crew are off!