The high winds at the end of the week took out a lot of services, difficult to be precise as for a lot of the time we were blind because power was off. However it seems like one effect was to completely take out the mast that we normally get our LTE from. Our router is now connecting to a different mast, about the same distance but completely blocked by our metal clad dutch barn. I've seen the router jump onto that occasionally under fault conditions, it gets a really poor signal strength and correspondingly poor performance. It's always used B20 in the past, the "different mast" has B3 but I've never managed to pick that up from here.
This time it's connected to Band 3, and although the signal is still poor RSRP -114dBm compared to -80dBm from the normal mast, it is actually giving us a really good speed. Download has tested between 35 and 50meg, compared to our normal of around 20. Strangely upload is slower, 5 instead of 10.
It's looking like it might be worth having another go getting our router high enough to see over the barn, or some location that looks past it. The mast is line of sight from normal eye level, although of course I don't know how high up the Three gear is.