The deal I was given from Global communications today was a one off lifetime payment of £175 for an 0800 number with 1000mins a month, I then set up my call diversion on BT to the 0800 number which is free (other than the £2/month BT diversion set up charge), the 0800 number then diverts to my mobile for free.
I currently pay a standing order to BT of £133/month and 90% of that is for call diversion.
You can see why it sounds like a very good deal!