I applaud you. When 5G comes in, we the unloved should all show BT where to stick it. Having got fed up of waiting for a fast fibre connection from BT I've had to get Virginia Media in. They talk a good game but the service is so unreliable I'm positive they are quietly remapping customers to slower switches (Traffic shaping) until you complain then they temporarily move you again. As with all the other providers they just keep putting up their prices but we are not gaining the rewards. I have TalkTalk with a landline that I need and broadband for just under £20pm but this is only able to provide 5.7Mbs so I also have VM just to provide what is supposed to be 100Mps for £25pm. I can't get rid of the VM and their unreliable service because when working as it should it's stilla million times better than TalkTalk/BT.
I'm seriously considering investigating your solution of I can move some of my reliance on the terrestrial link to cellular. Just need to check out signal strength and reliability properly