Astra's owner, Martin Jinks, has been in business for nearly 25 years. He was presented with the accolade by Which? chief executive Peter Vicary-Smith.
"Which? is important to businesses like mine, because it provides impartial advice and recommendations for people who are looking for the best products and outstanding service," Mr Jinks said.
"I'd like to think that the winning combination of high quality products and a service that is second to none is the reason we were selected as a regional winner.
"We install Baxi boilers that have been recommended by Which? – in particular the Baxi Duo-tec combi 28 HE."