Vodafone have just announced via their support forum that they now believe all Voice and Text services have now been resolved:
http://forum.vodafone.co.uk/t5/Latest-Vodafone-News/Network-Issues-Update-15-23/m-p/675383
They suggest that if you’re still having trouble connecting that you follow the instructions here:
Don’t forget, you can follow the tweets surrounding the Vodafone network outage on a map using our “Seek A Tweet” app :