DIY Home Automation, using a mix of Raspberry Pis (for "bigger things") and Atmega328p micro controllers (same chip used in the Arduino Uno's) - Goal #1 is to h

DIY Home Automation, using a mix of Raspberry Pis (for "bigger things") and Atmega328p micro controllers (same chip used in the Arduino Uno's) - Goal #1 is to have heating controlled by this lot.. So far, I've the heating relay control board done (16x 240V channels, controlling boiler activation and zone actuators to open the flow to different rooms). The on-wall thermostat PCB's are currently being manufactured, once they arrive I'll solder all the components in place and get a crude mounting done.. Then it's time to design the enclosure. Once all this is done, I'll move onto the lighting as Goal #2. For these, it'll be the ATMega MC's, some RFM69 RF modules, and either a simple relay (for on/off lighting) or some as-yet-to-be-determined dimmer circuit. The challenge for these is, there's A) no neutral wire in at the light switch in EU (or maybe just Ireland/UK?), and B) it's 240V supply or nothing - unlike the thermostats, where each is wired separately back to a central point, and can be swapped over to a 5V supply, these will need to drop the voltage on board using minimal space (much less than a typical 5V wall-wart).