I am hoping to remove most of the radiators from my system which is heated from the back of a solid fuel stove. I will be leaving the coil to the bottom of the hot water tank, and a medium single bathroom radiator in the system (removing the equivalent of 4 large single radiators). I am warned I need to take preventative measures in case the back boiler overheats. There is already an expansion tank attached to the hot water tank which was fitted when I had a solar water panel fitted. There is also an overflow tank in the loft which has a feed pipe from the current radiator system falling into it. I have been warned that because it is plastic, the overheated (boiling!) water might cause this loft tank to melt. I have searched everywhere for something which isn't plastic, but no luck. Any ideas? Can I replace the overflow tank with another expansion tank? Is there a fibreglass/galvanised overflow tank available which I haven't been able to locate?