We would suggest you select no more than three companies of similar size and send them any drawings (you typically need an architect to help you with these) along with a covering letter requesting a quotation. Include in this letter any specific requirements you may have, i.e., with or without decorations, the extent of wall tiling, with or without a fitted kitchen, etc. Also include a date for when you would like the quotation returned (usually 3 to 4 weeks at a minimum is reasonable) and a rough commencement date if you have one in mind.

The builders should, on receipt of the drawings, contact you to arrange to visit the property and take a look at what is being proposed and chat with you about the process. For example, will you remain in residence or are you moving out for a period?