Ipad works great on wifi, intermittent on PC with USB wireless adaptor

I have unlimited Fiber broadband in my home (I live in the UK and have Sky as my ISP) and my Ipad works fantastic. Great speeds throughout the house and upsatirs. My desktop PC however is located about 30 feet away from my router and on the same floor and is connected via a USB WiFi adapter (It is a T-Link TL-WN725N 150Mbps Wireless N Nano USB Adapter). My PC is intermittent. It always shows full bars but most times (its intermittent, at times I get 20mbg downloads) it takes forever just to load a webpage. I tried my Ipad in the same location at the same time and do not have this issue.
Before I recently moved houses, the same PC was hardwired into a broadband router (broadband lite connection) and the download speeds were more consistent than now with Fibre. Any thoughts?
 
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