Yesterday i had a whole run of images of generic aluminium cladding rejected due to the lack of a proper release. I thought only recognisable monuments where copyright under uk law. Does anyone have any experience with this?

Does it have any manufacturer's markings or is it identifiable as a type produced by a specific company either of which could lead to a rejection? I wouldn't worry about UK law its shutterstock's law that matters ;-). Monuments are not necessarily copyright though

No, they are all like the the attached image... bolted together and generic as can be straight out the panelling factory.  they already accepted the same location in monochrome taken last year...