FIXED!!!! Opened task manager and noticed my CPU speed was at 0.39Ghz which didn't look right. Googling that figure threw up lots more results. Downloading 'ThrottleStop' fixed the problem within seconds.
A really annoying problem that has only started in the last few days...
If I have my laptop plugged into the mains, it's great. As soon as I unplug it, every slows down. Things take ages to open and my internet speed takes a massive hit (a speed test with the power plugged in gives me 200Mbps, as soon as I unplug it I get about 50Mbps!)
I have Google