Mac mini 2013 wi-fi problems

Hey,

Currently running a 2013 Mac mini on OS X 10.10.3 and I'm having troubles with the wifi. Right up to the point where if I stand right next to my computer with my iPhone 6 I get 5Mb down on a 32s ping yet my computer is timing out web pages. Sometimes it hangs for ages then finally loads other times it works relatively normally. Anyone have any ideas?