If, as can3gxw has done, you install
DiskUsage, free from the Play Store, and select, "Storage card", (it is labelled that in spite of the fact it is internal memory), then under, "Storage card", it will show you how much free space you had after the OS was installed. That OS will include the carrier bloatware, etc; and disabling it will not gain you any more space as the phone has already been partitioned to accommodate it. The only thing disabling will do is to stop the app running and creating any files in the, "free", space. It seems that the OS on
can3gxw's phone is about 1.5GB larger than mine. This, obviously, cuts down on the available space for storage on the phone, initially.
Heh. This guy.
What firmware are you using anyway? Reason I ask is because I know that you can flash G900F firmware onto a W8. It's the same unit, really, aside from the W8 modem. Is it the UK version you're using?
The nice thing about the G900F model is that there are about 200 firmwares, worldwide, to choose from. Having been on Marshmallow on my unbranded U.K. model, for about 3 months now. I decided that in lieu of a more recent update for the U.K., (which is imminent), I would flash the latest unbranded firmware release for the Netherlands, yesterday. This has an English language pack, (all Samsung firmwares, do), this poses no problem for me. It means I can hop from latest release worldwide, to the next latest release.
You could flash a U.K. firmware, or any other G900F firmware, and then root your phone and install a custom recovery. Then you would need to extract the modem from the Canadian model and turn it into a custom recovery flashable .zip file. The only caveat is that usually the modem needs to be compatible with the firmware platform... i.e. Marshmallow platform -> Marshmallow modem. This would be something for competent and experienced flashers.