I have four 100 dollar iTunes cards which have all failed to be redeemed and claim the card is invalid, Please help

If you follow this link you should be able to get help from the iTunes Store:

https://www.apple.com/emea/support/itunes/contact.html

You're welcome. I've only ever had to use that link once, but found they responded fairly promptly (not sure if they operate 24 hours a day, or on American time), and once they did they quickly solved my problem. Good luck.