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The tank is a self insulated one, foam fitted.
I'm pretty certain that it is the lid where the water is coming from, it wasn't fitted tightly when I checked, I did remove it and there was a large, (about 2 inch) hole in it with a plastic sort of nut, which when removed leaves a hole for steam to escape I assume, I removed this and fitted the lid to the tank as firmly as I could, I will check later to see if it has made any difference.