For various reasons, it took a while to arrange for Terry to visit, but having done so, he arrived on time, made a diagnosis, ordered the parts and returned a few days later to make the repairs - which he did highly efficiently. This is the third time I have employed Terry and will continue to contact him. He is clearly very skilled and is remarkably friendly and helpful. He suggested a possibly cheaper option via the boiler manufacturers. I didn't take this up because when I contacted them they were distinctly unhelpful and in fact no cheaper - but I appreciated Terry's concern that I got the best possible deal.