Forgot to mention. Doing a speedtest speeds start off at 900 and then quickly drop to the final 500.

  @Sunshine It turns out the following is happening:

Ports 1 and 2 are full speed and I haven't seen a drop on these.

Port 4 mostly is at full speed but sometimes there is a drop.

I didn't check port 3

Ports 7 and 8 would mostly not even negotiate and when they did the upload speed was always 100Mbps. Even if I then swapped from 8 to 2 and back again, for example, 2 was always 900Mbps upload but 7/8 was 100Mbps. 

I didn't check ports 5 and 6

I couldn't work out how to connect the laptop directly to the ONT due to VLan id settings required by my ISP. However, given the tests above it seems some are negotiating at expected speeds, 4 is weird and I'm putting that down to "other factors". I suspect 5 to 8 are all the same and negotiation is always 1000Mbps down but only 100Mbps up for some reason. Certainly 7 and 8 do this. That's when they negotiate. More often than not they reported no connection.

This was with QOS -> Standard. I forgot to try QOS off though it is now and port 1 is still working as expected.

Regards

Damn it I forgot to add this information. Ignoring the ports issue for the moment. The upload speed starting high and decreasing is through Speedtest.net and depends on the server being used. Weirdly it happens on my own ISP's server (this never happened with the Netgear router) but if I change server the upload speed starts high @900mbps and remains there.

The speedtest built into the router is entirely unhelpful. I don't know which server that hits but am guessing it's a ZX81 on the moon. No way of changing server there. I hope QoS configuration sets things nicely (set to 1gbps up and down) and the router ignores the speedtest results.

This is really the end of this thread. I may come back to the ports issue at some point but for now things are working though I'm not entirely impressed with the software UX side of the router.