Simon Avery wrote:

Here's a question; Why do mobile phone charges cost more than
landline? Surely landlines require much larger initial investment, but
running costs must be fairly similar?

The landline networks were already built, the mobile companies are still
paying for their networks and licences.

The phones themselves are heavily subsidised.

Each base station has a limited capacity (far lower than that of a
telephone exchange) so you need more of them to cover a certain area.

If you were starting from scratch then arguably mobile would be cheaper.