QUOTE IS FOR LABOUR ONLY as i would cover all materials
That would be the deal breaker.
1. You WILL NOT have all the materials needed when they are needed so additional time needs to be figured while you go to get them. (My friend had to go 30 miles and it took about 2 hours round trip.)
2. Whether we figured $3,000.00 or $10,000, it would be immaterial unless you want to pay us travel time and per diem lodging and food. You need REAL prices from local plumbers who will actually be doing the work. Whether you get ripped off or not is up to you in your selection.
3. FEW plumbers will work for labor only, because there is not a lot of profit in labor once you calculate the overhead involved.
4. The only way to even start on a price for a remodel is to see the site. You will give the "best case" description of the project, but someone seeing the actual job might decide it is a "job from hell" because of the physical parameters.