my internet is stable enough, my bigger concern is that it is virgin fibre and I could disable it in seconds with a spade even in the dark. most people have sky or virgin and it is rarely a secret where these services enter the house. Anybody with half an idea could see where to cut a line.
I share that concern, but I thought I'd just add 4G failover. However, that's easier said than done, or it was in December when I looked at doing so.
Even if coverage isn't a problem, I found it almost impossible to find a decent router capable of doing it consistently. I always use Asus routers with Merlin firmware, and whilst they have failover, you need to use a USB modem which is not ideal for reception for me. There are some routers that will accept a SIM, but they don't appear to be that reliable, going by reviews. Netgear had device specifically designed to sit between the incoming connection and the router, but it had pretty terrible reviews. Shame, as this would be perfect. The only way appears to be to throw a couple of hundred quid at it, but I'll be having another look.