4G is very patchy outside and our walls are 1.5ft thick
I would still be strongly tempted to try going 4G if there is a signal even if it's patchy using a phone at ground level.
What I would do is go for say a Mikrotik SXT 4G kit mounted high up on the house on the outside pointed directly at the 4G mast.
and there is always the the LHG 4G kit for even more antenna gain.
Going down this route you should be able to get a reliable 4G signal.
Then run some exterior grade Cat 6 inside to a Ubiquiti EdgeRouter X SFP, to power it from the EdgeRouters 24V passive power over ethernet and put the Mikrotik into bridge mode. If anyone says that the Mikrotik can't be put into bridge mode that was only true of the now discontinued SXT LTE 4G.
For WiFi use one or more out of an UniFi AC Lite, UniFi AC LR or UniFi AC Mesh as required all of which can be powered from the EdgeRouter using 24v passive power over Ethernet. Noting that the AC Mesh is rated for outdoor usage should you wish to extend WiFi outside. You could power up to four WiFi points the 4G uplink and still have an SFP port which with an RJ45 SFP could be used for an uplink to a switch for more ethernet ports. Failing that shortly the EdgeRouter 12P will be available in the UK (though much more expensive) which has 10 ethernet ports that can do 24V passive power over ethernet.
There are options to use Mikrotik routers and WiFi points but personally I think the Ubiquiti ones are better. You could even use some random consumer grade piece of [censored] and a PoE injector to power the Mikrotik 4G modem but I would not advise that myself. My guess is that inside the house WiFi coverage is not grate so a decent solution is worth investing in. The Ubiquiti software has an excellent tool for predicting coverage so you can be sure to get good WiFi throughout the house.
If power cuts are a problem (often are in remote locations) then the upcoming EdgePower 24 (just waiting for stock to get to the UK) gives a nice integrated and efficient UPS solution by avoiding the inversion from battery to mains back down to 24V to power everything.
I appreciate the solution is not exactly cheap,but you get what you pay for and this is quality kit which would work and be supported for many years by the manufactures unlike the cheap consumer grade stuff that tends to be dropped after a couple of years.
Finally if some day you do get FTTP then you can simple hook the ONT into the EdgeRouter and off you go. Though the EdgeRouter X SFP will struggle with a full symmetric 1Gbps, but would be fine on a 330/50 connection. The EdgeRouter 12P on the other hand could easily cope with symmetric 1Gbps and then some though it only has 1Gbps ports.