We've been in this game now for 5 years and this is the fourth phase of this building project, each phase is about the same price. (Large site). We have been with this client since phase 1 and we also do other sites for them. This is hard work and payments take between 45-90 days, so you need to be pretty well established and have the cashflow necessary to pay wages etc.
Prices have also got to be competitive when submitting your tender.
You MUST have all the necessary documentation (H & S/Method Statements etc)
But the most important thing is to get onto the clients approved tender list. This will involve a full H & S audit by your prospective client and you normally have to score 80%+
and supply references and outside referees, good credit rating etc. I could go on and on, but once you have become an approved supplier and attained your position on the approved tender list, then all you have to do is be competive when submitting the tender.
It's not always the case of being the cheapest, it about giving value for money, and past performance.