should be in "build a jib 101" cult but seeing as im a fellow brit i know that the good stuff doesn't stay around for long so i understand your urgency!! get your self down to your nearby wickes DIY store, and grab 2 5metre orange drainage pipes, ziptie them together and you'll get yourself a nice shotgun rail, what i plan to do!
failing that nick a large black corregated gas pipe from a building site and jib that! hope your snow lasts!