Save up to % by comparing quotes from our suppliers! We cover aylesbury, high wycombe and the surrounding areas, for more information, please fill out our simple contact form alternatively give us a call on. With a westinghouse high efficiency heater % of the dollar spent on heating is properly used to heat the home that is real savings! upgrade your existing heating system with the combi wall and see how much you can save! If, following the assessment, it turns.