One of the (possibly beneficial) aspects of being Australian is the "hybrid" Anglo-American usage that we seem to have adopted over a century or so. So you choose the right keyboard, but spelling and grammar checkers can be tricky, and need to be nuanced.
You still need to store words like neighbourhood, organise, honour, practise as a verb, and so on. We still use theatre, centre, labour, and many others, but things are slowly gravitating towards US English, I expect.
With company plurals, I would speculate (with no hard evidence) that they are used equally, so:
- Manchester United (is/are) playing Real Madrid in Melbourne tonight
- Microsoft (is/are) opening a major new office in Sydney
- Ford Australia (is/are) leaving Adelaide in 2017
Either singular or plural would be used in equal measure in the media, and neither would be considered "more correct" than the other.
In terms of companies in general, I think size does matter a bit, but also (as noted above) whether the company name "sounds or feels" pluralish, and whether you're talking about the entity itself, or some elements within it.
- Baker's Delight is leaving the Metro Centre at the end of the year
- Baker's Delight are the biggest bread franchise in Australia
I expect that the answer is so context dependent that it's hard to be overly definitive.