in my opinion you should get rid of the plan to connect it to your home bi ... i dont see the point of doing this.
Has vodafone/o2/three/bt... already enabled 5G standalone in UK ? It would give you a much better experience with live streaming. Also a vendor called AVM is releasing a 5G SA compatible home router in the next months in europe. it should give also a better experience than any huawei router. But you can also just use a cheap 5G cell phone.. there are routers which can use usb-tethering. The market for 5G routers is small, there are only a few devices... also the SA compatibility is awful... iphone 12 still cant use it because apple dont release a firmware update. But UK is special... they are not using huawei backend equip anymore, so they have to use ericsson... this is a pain in the ass..
At the moment i am using a quite similiar setup, but i am recording to SDcard. It records around 30GB / day with h265 ... with dahua 5442. But it depends on settings...
Like
@sebastiantombs already mention.. you can control the bandwidth/data easily with reducing megapixel / framerate / codec / bitrate .....
with a 2mp camera with 15fps, 4096kbs max vbr, h265+ you will may end up with 5-10gb/day, depends on how much motion is there...
Also night with BW reduce the bandwidth alot... on night i am using around 80-100mb/hour
On my transitional home i am using a 4G router with a unlimited data plan, using around 3TB /month. But i think there will be problems with realtime live streaming... mostly ping is around 20-40ms and jitter <3ms ... sometimes there are spikes, which you would notice on live stream.. not often, but its there. that is a problem you have do deal with when using 4G.
using p2p bridge with an existing internet connection would be much easier than 4G... less ping and jitter (spikes)