Well it now seems that Manchester T/S (after I argued with them) have wrote to MicroDirect and informed them of their misleading 'National' description.
Looking at their
website now under customer services, it reads:-
Quote:Tel: 0870 44 22 233
Please note: Numbers prefixed 0870 will be charged at no more than 8p per minute at peak times, 4p in the evenings and 2p at weekends from a standard residential BT landline. It doesn't seem to mention that costs from other landline/mobiles vary but it does clearly state that prices they quote are from a BT landline. A small victory I believe.