With all the major companies I have worked for if a new customer did not show reasonable credit worthiness then the full amount would be payable before commencement of erection. This included firms such as SGB, Palmers, S&C, and Bow Scaffolding.
Normal trading terms for established customers would be 70% on erection, 30% on dism - payment within 1 month of invoice.
Obviously large and complex projects would be charged on a monthly interim basis, subject to survey and agreement in line with the order constraints and the legal rights afforded under the 'Local Democracy Economic Development and Construction Act'
As Dandaps shows above though, supply and payment still comes down to what the two parties agree to do, and then do!