An update after several months of EE 4G...

Sometimes it worked fine for a day, then I got periods of several hours with lots of packet loss. I've also found that the antenna position can make a huge difference. It was in the corner of the window sill, but placing it in the middle of the window and mounting it horizontally, rather than vertically seems to be better.

I've now got it on band 3 as that was doing better than band 1. Last time I posted I locked it to band 1 as it kept alternating between the two bands, but when it did, the band 3 performance was very poor.

Anyway, it seems to be working nicely, for now.