We have gone with Bluewater for our narrow boat build. We have visited the boatyard (and others) on several occasions during open days and alike, looked at the build quality over a number of years and compared joinery etc. with other builders, have been impressed with the workmanship at all stages of build. We also read the negative stories within this forum and decided not to make a decision based on that alone, but to take them in context with what we had seen and been told by other owners. Take the opportunity to speak to customers that have had boats built by your shortlist builders, we did and found that was a great way to find out unbiased opinions, our experience so far is very positive.
My advice is to know what you want and research as much as possible, so you know a little of what you will be talking about if you don't already, this forum has a great source of material for that.
Good luck with your project