Used one of those heaters in my uninsulated 35' boat in the bitter cold of SF Bay winter. Worked fine. For England, think you'd need at least two of the heaters. FWIW, lived aboard a Norfolk, VA winter that would probably be closer to England's with electric heaters. Condensation was a major issue. Every surface of the boat was dripping with moisture and it pooled in low areas. Would think about a vented 'dry' heating system for the times that you are on the boat.