Will depend to a degree as to where you live in the country. Also how much leg work and effort and time you are prepared to invest personally. Yes, you can get some cracking deals on materials if you shop around. For most tradesmen, time = money and the amount saved can be offset by the time spent researching, specifying, ordering etc.
If I was taking on that job and you wanted to buy the materials, I would need to spend time putting a cut list together. Time being the operative word.
If you’re not willing to invest any of your own time, then suck it up, get a few quotes and pay a professional to do the whole job to your requirements. It’s really that easy.