I'm about to order a 3m2 panel from Viridian Solar http://www.viridiansolar.co.uk/About Viridian Solar.htm The panel replaces the roof slates and is very discrete and low-profile, the system is fully self-contained and automatic and drains down when the panel temperature goes outside preset limits to prevent freezing or boiling. I've already installed a 160 litre copper cylinder in the attic in tandem with the existing house cylinder and fresh water has been feeding into our main cylinder through this with no ill effects for over a year. All I have to do now is install the panel, which will pre-heat the water entering the main cylinder. I will also plumb the flow and return pipes with a motorised Y valve so that when we upgrade our main cylinder soon to a bigger size with a faster coil we can run solar heat into a second coil in that cylinder as well, potentially storing up 230 litres of solar heated water. Here's a pic of the system, the cost with a 3 m2panel will be around £1600. http://www.viridiansolar.co.uk/Products_Solar_Plumbing_Kits.htm Anybody else done anything like this? Any hints? Tips? Experience?