Ethernet Speeds OK, WiFi speed ridiculous

[#1]

On day two with plusnet. As expected, the speeds have fluctuated, however my wifi speed are ridiculous. I'm getting around the 50mbps wired but only 1-3mpbs via wifi. I have tried different channels with no luck. I'm sitting right next to the router also. Any suggestions?

[#2]

Download a sniffer app, I use WiFi Analyser on an Android phone. This will enable you to see the strength of your WiFi transmissions compared with neighbours and select the best channel. It could be a faulty router. The other thing to try is to separate the 2,4 and 5 GHz channels. This should help with this:  https://community.plus.net/t5/My-Router/Making-5-GHz-have-separate-SSID-with-the-Hub-One/m-p/1349587....

[#3]

A friend of my had the same issue a couple of days ago.
Turned out to be a faulty USB WiFi dongle which we proved by plugging it into a known working system.