Yes, we’ve been with Free Mobile for ten years now and I use a couple of their SIMs for faultless 4G internet, 40Mbps no sweat compared to sub 1 Mbps on copper. I don’t need fibre speeds, in fact IMHO 99% of the consumer world doesn’t need fibre speeds.
Absolutely Graham, I have been caught up in that rubbish, Orange arrive and say the outside line is fine and Bouygues or whoever pitch up and say the internal connect is fine and you’re left piggy in the middle. Both engineers outsourced and uninterested wasters BTW. After going around the loop twice I went put in my own 4G solution which is rock solid. As they say, in any contract you need one throat to choke 
I’m on the brink of changing my internet service, thought about the 4g option, but the services I looked at had a cap of 200gb. That would be fine for my personal use, but just wouldn’t be enough to run the security cameras.
That’s why I’ve two SIMs, 420GB per month I think for 40 quid. That’s enough for us with a lot of stuff on Onedrive, iCloud and four external Blink cameras.