Thats a good point! Normally when testing it is the wireless i use as my laptop and my dads pc is wireless and it is rare i use the desktop which is RJ45.  Wonder if that helps hmm.  Very annoying problem as sometimes it stays connected for ages then every phone call knocks it off. and because it's so random testing each part is tricky to narrow it down. I have a horrible feeling it is the extension cable for the phone 
 
Thanks for the replies!