Rounded Developments Enterprises and the Eco Home Centre have collated a list of independent companies who are based in or around SE Wales who proport to be able to assist you with your building projects. RDE takes no responsibility for the content of the any of the websites listed, nor for the products and services provided by the companies. However it is a good starting point.
Also if you want your building work to be insured look for the Masterbond Trust Mark that is available through the Federation of Master Builders. This can provide you with a short or long term insurance against workmanship issues. Look for following logos: