By Kate Holton, Natalie Thomas and Hannah McKay SWAFFHAM PRIOR, England (Reuters) – In a quiet field in eastern England a vast heat pump generates enough warmth to supply houses throughout a historic village, a pilot project testing ways to spur renewable energy use in a country that is falling behind its net zero targets. Resembling a large agricultural site, with gleaming silver water vats, the heat pump produces water hot enough to feed existing domestic systems, removing the need for costly home retrofits. A 60-year funding scheme removed upfront costs. Supporters say the network, the firs…