As you think about the build, a few pointers that you should consider:
1. Ensuring in your tender process that a performance bond is provided by the building company. This effectively is an insurance against poor work, the work not being completed, the company going bust etc. The insurance provider undertakes a significant level of due diligence on the building company - checks financials etc and it is also the building company who has to take it out and the cost of it.
2. Any contract that you enter into commits the Directors of company also, so they are personally liable in case of issues
3. Details of each person on the team doing the actual build in terms of qualifications for work they are doing, length of experience etc. Most companies will have a number of teams and the quality varies considerably between them.
Any reputable company would find the above conditions standard.
I have used a few building companies, including APT and happy to provide a perspective on our experience with them, if helpful.