Isn’t this question asked on this forum every few months? It’s easily searchable.

To be fair, TalkTalk’s help desk can be very hit and miss. But also it’s also true that there’s almost certainly nothing the OP can do about this.

Does it have a low voltage disconnect? Because it’s not good for batteries to be pulled too low.

I got my DC UPS from AliExpress for not much, but it’s interesting to see something handmade.

I have gigabit cable and fail-over to VDSL2.

I use a UDM-Pro with dual WAN configured. I previously used PfSense with load balancing and feel it did it better than the UDM-Pro, but there are other benefits to the UniFi ecosystem.