I've realised that my sore throat could be caused by my duvet cover. You see I haven't used this duvet cover for a while and it's been in storage. I didn't wash it and my sore throats started after I change my bed linen. So I guess it's pretty obvious. Unfortunately by the time I realised this it was passed midnight and my I could get to my other bed linen. The airing cupboard's in my flatmate's room and he'd passed out long ago.

Let this be a lesson to you all.