Updated iphone 6 with 8.4 and home screen now massive

I have installed 8.4 on my iphone and immediately the home screen was massively enlarged. I can't put my passcode in to get past the home page to look at settings as the screen is so big it only fits one number on and when I try and scroll across I hit other numbers. I've tried holding the home key and power key and rebooting this way but it doesn't change anything.I've connected to iTunes on my PC and tried to do a reset this was but it's asking me to turn off Find my Phone but I can't as I can't get past the home screen. Help would be great!