G'day Drymouth, sorry to hear you're having so much trouble with this.
First, lets get your actual condition diagnosed: An apnea is a cessation of breathing for 10 seconds or more. So 400 central apneas and 80 obstructive apneas adds up to 4,800 seconds - but there are only 3,600 seconds in an hour. Something doesn't add up! Maybe it's 400 events per night? That's still severe apnea (eg 480 events over 8 hours sleep is still an AHI of 60, which is very severe). You need to get hold of your sleep study records - if you went to a private practice they are required under APP-12 of the Australian Privacy Law to provide it to you unless doing so would endanger your health or sanity. See here: https://www.oaic.gov.au/individuals/faqs...lth-sector
With all the other medical issues it's not surprising you don't feel too flash.The apnea may be making some of these issues worse, or it may be the result of some of them. Either way, I think it's for certain you're going to need an ASV machine to treat your central apnea. The ResMed S9 VPAP Adapt or the new Resmed Aircurve 10 CS Pacewave are excellent machines. Alternatively you may try the Philips Respironics Bipap ASV Advanced (I think that's what it's called). These are all expensive machines - your talking around $4000 or more, maybe less if you can find a pre-loved machine at a reputable seller such as dealer #2 on our suppliers list: http://www.apneaboard.com/forums/Thread-CPAP-Supplier-List
The HC150 is a stand-alone humidifier which is separate from your CPAP machine, but which is advertised as being compatible with most cpaps. I suspect it is superseded as it's no longer listed on the Fisher & Paykel website. If you're looking to import one, ensure you get the proper voltage, as the American version is noted as strictly 110 volts only. Now, having said it's compatible with most machines, I would have my doubts that it's compatible with an ASV. These machines rely on continuous real-time monitoring of your airflow and respond instantly if there is a disruption to your breathing. I don't know how well they would work with a big bulky humidifier in the circuit. (In fact the Aircurve probably won't work at all as it has a built-in humidifier which the HC150 is not compatible with).
As mentioned above, can you tell us which model Resmed S9 you have now? It will be printed next to the on/off button and will be something like Escape, Autoset, VPAP Adapt etc. Also, download the SleepyHead software (link at the top of this page) and upload some screen shots so we can get a more detailed look at what's happening.
Hang in there mate - we'll help you through this.