If creaking is the only problem (as opposed to flex), check with BF. There are probably some components that need to be greased or tightened. Happens all the time on my Swift.
I know Swifts are built solid enough that you can stand and/or pull on the handlebars; I assume this is also true for BF and other expensive folders / separatables (Moulton, Airnimals etc). Not a good idea on the low-end Dahons though, since the handlebars are very flexy.