Just googled "BT low user scheme" to see if the scheme was of use to me.
One level down was
http://www.bt.com/customerservices/cust_details.jsp?BV_SessionID=@@@@1436337005....Quote
Calls
With an In Contact Plus line, you can make the following calls free of charge:
Calls to the emergency services on 999 or 112
Calls to BT on 150 (for Customer Services)and on 151 (to report a fault on your line)
Calls to freephone numbers e.g. 0500, 0800 and
0808End Quote
So that means you should be able to use 1899 etc 0808 access numbers for a cost of
...............Quarterly rental
BT will send you a bill every 3 months for £10.75 which covers the rental of your In Contact Plus line. If you would like, we can make it even easier for you, by allowing you to pay your bill in advance. Simply ask for a BT Payment Card.
End
£33 normal quarterly rental
£10.75 LUS rental
£22.25 saving
2225 mins or 37 hours and 5 mins using 1899 etc (NOT allowing for connection fees, depends on your call volume) before you reach the same price.
If you used 1899 to a max of 1 hour per call it would cost you 63p per hour, mins + connection.
£22.25 / £0.63p = max of 35.32 hours. Or 35 hours and 19 mins per quarter.
OR
You could use the Voipstunt (for example) callback service at a cost of €0.05, about 3p per call.
£22.25 would buy you 741 calls to UK and several foreign landlines. Each call permitted up to 1 hour before disconnection.
741 calls / 13weeks = 57 hours per week (using maximum call time)
As this slightly exceeds the 5 hours in a 7 day period allowed by Voipstunt, this wouldn't happen.
So if we assume you're going to get as much as possible for the same money.
5 hours included. 5 * 3p = 15p
extra time is charged at 0.93p per min. Therefore an hour is (60 * 0.93p) + 3p = 58.8p
£22.25 - 15p = £22.10
£22.10 / £0.588p = 37.59 hours
Or 37 hours and 35 mins.
So... If you do less than 741 hours a QUARTER on calls you could be better off using their Low User Scheme
For those who weren't aware, and I've only just read it, of you use over 5000 mins monthly, you can buy UK landlines at 0.6p per min. Doesn't if this is plus or inc vat. If plus, then it's a total of 0.71p
http://www.voicetrading.com/en/rates.html