To feed power directly to the Raspberry-Pi board without using the micro-USB connector, I soldered 2 wires directly to the back of the circuit board.
The connection leaves the fuse and reverse-polarity protection diode in circuit.
A couple of small holes drilled into the side of the case to form a slot brings the power wires out.
Heatshrink over the wires protects them and tidies it all up.
Now to test it.