Available versus predicted
Many / Most people commenting on IoT seem to be hobbyist of some sort or perhaps working on a single fixed installation. If you're designing something that needs to go out there and work in not-predefined locations reliably, LoRa is right out. SigFox actually has decent coverage depending on region but the data amounts are simply far too small for anything doing regular monitoring.
LTE CAT-NB1 and LTE CAT-M1 are not here (in UK), period. No amount of handwaving gets around it, you design a device with either and you just made an expensive paperweight which might start working sometime in the future, or not. CAT M1 was "supposed" to work on existing basestations with just firmware updates but this didn't happen, surprise. In reality, you need hardware changes which means there's nonzero cost involved and operators don't wanna since there will not be that much business for some time. And since the network isn't there, business won't come.
So for UK, for something with real coverage and reliable service, you've got two choices really. There's LTE CAT-1 which is a slightly cheaper-to-implement low speed (around 10Mbit/s) version of common garden 4G technology. It works with zero modifications on 4G networks, which is nice. What's not so nice is that you've now got a bona-fide cellular module that will do around £20-30 worth of damage when bought in volumes. Ouch. If you're deploying in US, you may very well get a reasonable M1 coverage which slashes module prices to one half or less.
The fallback is the good old GSM GPRS. It's everywhere and it works. It's slow but the ~8kbit/s speed is a far cry above what you can achieve on SigFox and you can push data all day if you want unlike LoRaWAN. If you can get EDGE, you're in with roaring data rates.
3G is on it's way out in intermediate term, better not bet on it for something that needs to be around for 5-10 years.
So the sad truth is that if you need a serious IoT device deployed right now in UK, you've got to reach for a 20 year old cellular technology. Where's my flying car?