Andy

Thanks very much for your response, it is very helpful. I hadn't actually considered a direct immersion heater but now that you mention it, it does make sense. I know that the immersion will take longer to heat the tank up but it's something I will consider now. We also have a wood/coal burning fireplace that will be replaced with a multi-fuel stove at some point, and the 'in laws' have a pile of dead trees for us to burn (as long as we chop some wood for them too!) that provides additional space heating.

Thanks also for the advice re heat plates. As we have a suspended timber floor the noise/creaking could be an issue. We should easily be able to use sand/screed to fill the void as the timbers rest directly on concrete upstands at regular spacing, hence no need to beef up the timbers.

I have a form from the local electricity board and will be sending this off shortly to confirm acceptable load. My electrician will be helping to fill it out so will get an idea of what we can install shortly.

Thanks again for your help on this

Nathan