Hi, came across this just now and ends in less than an hour so hopefully some will benefit. (Edit - it seems that if you refresh the page the countdown goes back to 1 hour so looks like it will probably last longer)
Dont forget the voucher code to get a free Nokia 3600 as well. (Edit the coucher code is shown on the bottom left of the offer page and is free3600 :-)
Seems a great deal for just £15 per month
Sorry if there are any mistakes in this post as I had to rush it !!!!