Hi everyone - new user / first post.

All connection speeds here are taken from the various router web interfaces, not from speed tests.

I was connected to BT Infinity 2 for around 18 months. The connection was around 74-76Mbps down, solid 20Mpbs up.

Two weeks ago I switched to NOW TV Super Fibre, which I assume is an identical product to Sky Fibre Pro.
During the order process the speed estimate was 78-80Mbps, with the minimum guaranteed speed at 73.7Mbps.

On switchover day I disconnected the BT Hub and connected the NOW TV hub. It connected at 64Mbps.
I kept an eye on the speed, expecting line testing to occur, but the hub did not disconnect once in 6 days - the speed stayed constant.

Fast forward a week, and we've had two Openreach engineers out, we've had our cabinet port changed (?) and various line tests and resets carried out.
Openreach can't find a single fault on the line. I can see the cabinet from my window. Nothing has changed except the router and the ISP.

The speed is significantly below the guaranteed minimum, and I have a third engineer appointment on Thursday - though I'm not clear what this one will do that is different, but NOW TV said this was the last option.

Has anyone else experienced this? The physical line hasn't changed, but we lost 15% of our download speed in the space of a few minutes.