I have been trying to obtain a lantern to replace the existing, rusting, one. Problem is that all available ones are made with the lighting section above the fixing, whereas he existing one is below. This means that the light will be too high above the door.

I suppose I could replace with a solar lantern, but how do I seal off the cables? I don't wish to pull up carpets and skirting boards.

Many thanks.

If you are talking about temporarily sealing the wires you can go with wire nuts made for wet locations. Put a nut on each individual wire first insuring the power is off at the panel. If this is a long term seal until a new fixture is found you can add an exterior grade weather proof box where the old fixture was attached. Any chance of finding a fixture that will look good/work if mounted upside down?