Hey there Adam193, welcome to the Community. I've taken a look at Vodafone Ireland's offer and it seems they're being quite nice. All you need to do is cancel your Premium subscription and then take advantage of the fantastic €5 offer! You can find out more information at: https://www.vodafone.ie/red/extra/spotify and at: http://bit.ly/1MNIR4w
I hope I helped. If this doesn't work, please feel free to reply to this post and someone else might be able to help you! The Community is great for helping others, discovering new music and making new friends. Feel free to explore, and I look forward to seeing you on the forums some time! Good luck with getting your €5 offer and rock on!