Solar generation, Home Easy units, and Jeenode remote switching

This is my first post, apologies if this is in the wrong forum. Sorry this is a bit long winded but I felt I needed to give some background to the project.

We have a roof mounted solar array which can generate up to 1.48KWp. In the UK, power generated by domestic mains-tied PV systems are supported by a Feed-in Tariff payment per kWh . In addition there is an additional payment for electricity fed back into the grid. For small PV units the amount is not metered but assumed to be 50% of that  generated.  I am attempting to make a set-up which will enable this “surplus” to be used, rather than exported.

There are existing units which enable this to be achieved but these are expensive and most have to be wired into the mains supply.

I wanted a design which could be safely carried out by simply switching a Home Easy plug adapter (HE302S). I initially used a dedicated circuit and LDR, to monitor the mains supply LED. This pulses once every 1Wh used. However when there is more generated electricity  than electricity being used, the LED is continuously on.  The circuit detected this and then, via a relay, actuated a Home Easy magnetic switch (HE305). (This was modified by removing the reed-switch and extending the contacts to the output of the relay)   This sent the ON command to the plug unit, which switched on a low wattage (850W) kettle.

 It worked, but there were two problems. In the case when the generated power only just exceeded the amount being used, the additional load immediately exceeded the threshold, and the kettle would be switched off. This caused unwanted cycling. In addition the range of the Home Easy unit (433.98MHz) was variable and often failed to switch.

I decided that the Jeenode would provide a much more flexible solution and a better RF range.

My starting point was a sketch based on http://www.open-electronics.org/real-time-energy-monitor-with-arduino-and-labview/.  With some modifications this is now working and can generate a value for the average power being used over a minute. A potentiometer is used to set a generation threshold above which the Home Easy plug needs to switch on.  This can be set with a sufficient margin to, in most cases, prevent cycling.

However, the next step, is to add an additional pulse monitor on the mains supply meter LED. In the event of an additional high load item (immersion heater, for example) being switched on this will immediately switch off the Home Easy plug, and switch it back on when the additional load does off.

Once working I am hoping that I will be able to send a simple ON/ OFF command to the Home Easy plug unit. As the frequencies are not compatible I still intend to use the Home Easy magnetic switch arrangement, but driven from a relay at the output of the remote Jeenode. This should overcome any range issues.

I am looking for a simple way of remotely actuating this relay using the RF12 protocol, but have not discovered any information how this might be achieved. Any help would be most useful at this time.