Probably about time I posted here as this has been going on for around 2 months now.
Recently my internet has been really spiky, even when it's 'good', it'll freeze up for around 0.5s every 5-10s which, while it's not the end of the world, it's still pretty annoying and a performance decrease while raiding and makes more reaction based games (ie League) pretty much unplayable.
Running a speed test while it's good usually results in around 20ms, 50 down and 16 up.
Other times it'll be awful. Speedtests will say <5 down and ~5 up and the ping will range anything between 50 and 800ms. In WoW, I'll be on 1k-5k ms.
Small thing to note about the speedtests, I live in England but the site shows I'm in Ireland and connects me to an Irish server. This doesn't make a noticeable difference in speeds though and gives me similar results to if I test a local server.
I use wireless but, while it's running slowly, if I plug a laptop in to the router I'll still get awful speeds, so I'm pretty sure it's not a wireless issue. Similarly, I'll get problems even if I'm the only person connected. I also tried swapping the cables that connect the router to the modem and the modem to the wall.
Any help would be much appreciated and feel free to ask for more info. Really want to get this sorted before looking for a new guild and to start playing League.