As Graham said in his OP, there are some very interesting possibilities on this service if one can call 0843 numbers.
The problem is, as mdsaleem123's post hinted, it is neither easy nor cheap to call such numbers from a mobile ( even if the networks have opened such number ranges in the first place ! )
What I have been looking for is some subscription service, which can be called from a mobile, which will allow 0843 calls AND charge for them at something like BT rates.
If anyone know of such a service, please will they kindly let me know.
TIA.