so, just been testing it and the cable is an old 100mb cable. So I have ordered a new 1gb one.
This should take me a step forward at least, though it doesnt explain why the wifi on my phone works at 150mb but on my pc only 80mb.
A cable which doesn't have all four pairs connected, or is of the "crossover" variety, supports only 100Mbps ethernet. You can easily check if this is the case by looking at the network device settings and see if it has negotiated a 100M or a 1G connection.
By the time you've taken off IP and ethernet header overhead, a speedtest service will report just over 90Mbps.
Any less than that will be due to Windows overhead, poor NIC device drivers, antivirus etc.
Wifi isn't going through that ethernet so it can do whatever the wifi can do. Wifi 5 (802.11ac) typically achieves around 400Mbps real-world throughput if you're very close to the router.