Please don't click cold without actually reading! Sorry if this has been posted before, but I could not find this particular deal.
I recently moved house, got myself cheap line rental from Primus and then started searching for the best broadband only deal that I could find in my area.
If O2 supports your area this deal might be better for you: http://6monthoffer.o2.co.uk/
Anyways I digress, I came across this deal and figured it was pretty good, you need to to be an existing Orange customer for this price which I am not, however a mate is a PAYG customer so I gave them his number and the order went through fine for me.
At £10 a month with a £40 voucher combined with unlimited usage I could not find anyone cheaper, hope this helps someone.