Hi Hippymum. Are the bumG's fitted nappies, or pockets? I have bumG pockets and I don't use a liner with them as they already have fleece built in. My itti bitti is a fitted, and my bubblebubs are all-in-one's. I use microfleece liners for both. They help protect the nappy and its easier to get the poo off. Though with NB poo, it'll be pretty messy regardless, LOL! You can make your own liners by cutting strips of microfleece (which you can get from shops like Spotlight - do you have Spotlight in Perth?)
You can get flushable paper liners for your nappies, but IMO they're not very useful until bubs is on solids and doing more solid poos.
GL with it all