The battery-powered measuring device (transmitter) was very easy to install (with a clip around the incoming mains feed from the meter) and the receiver unit seems to pick up the wireless signal anywhere in the house. The receiver is powered by a mains adapter but I wanted to run it from my UPS (which powers my server) and it turns out that it runs off a nominal 3V DC at less than 80mA. It also has a serial port which pushes out the measurement data (including temperature) every few seconds.
I found a very convenient USB-serial adapter device (ByVac BV103) that matched my needs exactly because it can operate at the 3.3V signal levels that the CC128 puts out and
has a 3.3V supply derived from the USB connection that can power the CC128 - perfect!
The BV103 contains a FT232BM chip and the FTDI drivers for that seem to built in to my Fedora distro so it was plug-and-play in that respect. I had to write a little code to set the baud rate up to 57600 and then I just grab about 45 second's of data every 5 minutes (in XML format as described on the Current Cost web site) and process it. The temperature reading is normally meant to be used for checking your interior room temperature but, as I've put mine near to the server in my roof space, it's a handy bonus for checking the conditions in that particular spot.
The wiring details are described below:
CC128 RJ45 - pin 8 (DATA) to BV103 - pin 3 (RXD input)
CC128 RJ45 - pin 4 (GND) to BV103 - pin 9 (GND power)
CC128 power connector - inner to BV103 - pin 6 (3.3V power)
CC128 power connector - outer to BV103 - pin 9 (GND power)
The picture confirms my reference for pin 1 on the RJ45 to avoid any confusion and the details of the BV103 can be found in the datasheet on their site.
I installed the BV103 into a small box and connected it with a standard USB cable and the result is fairly neat and tidy I think.