Alex, I have seen/heard a few with a similar creak, if you can get a can of motorcycle chain lube (good for rear springs also) and spray around the base of the front suspension main springs where they rub at the lower point and up to where they rub up against the dust cover at the top (under the crosshead upper lug) whilst someone is turning the steering lock to lock you may find the noise goes. Needs doing as part of the regular service, just ensure you don't get any overspray on the brakes.
