@Russell67
What about the 2.4GHz wireless speed and the wired speed from the TP-Link powerline adapter? Are they normal?
What is the light status of the TL-WPA8630P kit?
Try to change another wall socket to plug it and ensure that the powerline light is yellor or green; then please test the speed. In the meantime, please click here to check the wireless link speed of the 5GHz connection. And please verify the powerline link rate on the tpPLC utility.
And you can try to plug the adapters into the same room to avoid the powerline noise and test the actual speed you can get.
You can follow the below instruction to narrow down the issue also.
https://www.tp-link.com/support/faq/2231/
Any updates, just let us know.
Good day.