Ponders OK. I see. Must admit the few times in a year I dial an 0845 or 0870, I do notice a "hit" on the Primus bill, but the saving in line rental of some 5 quid minimum per month (and now they have dropped the rental a few pounds, will be more) adequately compensates for the times when I have had to pay for a call or two.
Think there are "pro"s and "con"s relating to any of these services... in particular with Plus.Net, BT (and even Primus, for those paying more than a tenner a month) there's the "annual" option where the line rental is reduced somewhat (but if you leave at any time other than the anniversary of paying, lose out as there is no refund... a ploy, I think, to avoid Ofcom's ruling on how much a telecom firm can charge for remaining months of service, if user switches firm during the contract period). I think it's a pretty big 'con' to have to stick with a company for 12 months to get the price down significantly (when Primus is willing to charge a fraction, and even offered the 5.99 rate to me, when my spend with them has been under a fiver on calls in the last 12 months ).
For example, something which would interest me if I was with BT for line rental, and had "anytime" calls, would be their recently introduced BT SmartTalk where I'd be able to use an App on my Android phone to make calls "from" my landline number. In other words, calls to 0845, 0870, 0800 and other landline numbers could be made from my mobile via the internet and "billed" {or not!!} to the landline account.
I have unlimited data with Three mobile, but only 100 minutes a month of voice calls, where I used to have 600 on a previous contract with Three, and then unlimited calls with T-Mobile {but they removed some masts and I had major problems so they let me cancel the contract with 6 months left to run}. So you can see that getting calls via the landline (at least for calls to landline numbers) could be advantageous, allowing me to keep my 100 minutes for calls to mobiles.
On the other hand, I'd be spending a small fortune to have BT line rental and "anytime" calls, and can get 150 minutes of calls + 250 texts, each month, from Ovivo, with just a one-off 15 pound payment... so I think I will forego the chance to try BT SmartTalk and get a 15 quid SIM :)