To be honest TJ, the time it takes them to pay isn't (often) out of line, but its still time, whether its a small amount of time or a large amount of time doesn't matter. The presumption with public sector clients is that the supplier will provide goods on credit, regardless of whether the supplier is offering credit or not. Its funny how many public sector organisations I've worked with who find themselves blacklisted by their regular suppliers not because they don't pay/pay very late, but because they pay within their own terms rather than within the terms their suppliers offer.
Because the nature of my work is very diverse I'm almost always sourcing services and materials on a once-only basis, so I'm having to get my supplies on a cash basis, but provide my service on a credit basis, so for 30 days from invoice plus the time between me buying things, doing things to them and delivering them I'm a bit cash poor, if the jobs bigger than usual, or if two or three jobs are running in parallel then it gets a bit sketchy, as they are now with three jobs all kicking off at the same time, to be delivered at the same time and all quite spendy.