Managing director Jonathan Hey, who founded the Essex-based company 20 years ago, said the business was establishing itself for high quality bespoke garden rooms, orangeries, pool houses and roof lanterns.

Turnover for the first half of 2012 was up 41% on the same period a year ago and had already outstripped total turnover for 2011 by 20%. Mr Hey said figures continued to look strong and the volume of orders was up 20%.

About three-quarters of its business was windows, with the remainder external doorsets, such as French and folding/stacking systems. Westbury typically completes 50-60 projects a year.

Mr Hey said the company had benefited from an elevated product and targeted specification, and investment in technology with a newly completed £2m larger factory in South Woodham Ferrers. He added that the addition of John Mumford and Chris Wood, formerly from Mumford and Wood, had sent a clear message of the company’s determination to sell high quality products.

"We’ve created a five-year plan to develop the business to a controllable size, using available capacities without stretching volumes or compromising quality. I’m particularly heartened by the variety of clients we are attracting and this should stand us in good stead for future growth and minimise any potential risk from the economy," Mr Hey said.