Extention

I am looking to get a home extension built with the dimensions of less than 500 sq ft. I have a rough idea of what I'm looking for but I'm open to suggestions on the design and style that would work best. The extension will need to meet all the building regulations and have fixtures and fittings that are up to a certain standard. I am looking for a professional who is experienced in constructing home extensions that is able to provide detailed plans and a firm quote for the project. I am looking for a fantastic end result and timely completion of the job.