There are some interesting notes in the price list:
https://www.southern-electric.co.uk/uploadedFiles/CoreMarketingSites/Assets/Docu...

2.3.1 - 03 Numbers
The 03 prefixes denote a non-geographic number treated as if it was a call to a geographic number for the purposes of charging and inclusion in call packages.
The cost of these calls is shown in Section 2.2.
Please note that some organisations providing 0845 & 0870 numbers to contact them have now transferred their contact numbers to use the prefixes 0345 and 0370 respectively instead.

2.3.2.1 - 0845 & 0870 rates
0845 and 0870 numbers are country-wide NTS numbers, often used as contact numbers by service departments of large companies and by public service bodies.
Please note that some organisations providing 0845 & 0870 numbers to contact them have now transferred their contact numbers to use the prefixes 0345 and 0370 respectively instead. Calls to 03 numbers are charged as geographic calls as discussed in Section 2.3.1.
Calls to dialled numbers beginning with 0845 & 0870 are free (up to 70 minutes) during the same inclusive periods of your call package for local and national calls.

which means there is NO excuse for this:

For any further talk enquiries please call:
Southern Electric 0845 678 0051
Scottish Hydro 0845 678 0052
Swalec 0845 678 0053
Atlantic 0845 678 0054
SSE 0800 048 2394

As expected there are multiple places where 0845 and 0870 calls are mis-described as:

Non Geographic Local (0845 numbers)
Non Geographic National (0870 numbers)

Its only £5.99 per month to take a 12 month contract with Primus through Moneysavingexpert.com for line rental or £6.99 per month for a 12 month contract with evening and weekend calls included.  This would appear to be a great deal cheaper than the Southern Electric deal for anyone who objects to BT's exorbitant £15+ per month line rental for almost nothing other than inclusive weekend landline calls.

See http://www.moneysavingexpert.com/phones/home-phone-calls#cheapline

The only thing to watch out for with Primus is that they have something of a reputation for unreliable billing, although this mainly seems to relate to broadband where they don't advise customers if they exceed their monthly data cap and then have very substantial charges if you beyond that cap.  Their customers services also reputed to be very difficult to get through to on the phone.  There is however an email address for their Chief Executive at:-

http://www.ceoemail.com/s.php?id=9624

See http://www.moneysavingexpert.com/phones/home-phone-calls#cheapline for more details on the Primus £5.99 and £6.99 per month packages.

The only other point to watch out for is this appears to be a special cheap deal for new customers of Primus via MoneySaving expert.  In Year 2 expect them to charge you their regular monthly rate of £11.39 per month for evening and weekend calls as currently shown at http://www.primussaver.co.uk/HomePhone.aspx  However this is little more than the Southern Electric deal after a much cheaper first year and includes all your evening and weekend calls although about the same as BT's Line Advance Deal for 12 months up front although that only includes Weekend Calls.