You could take it to the manager of the department that you actually would be working for...you might want to go so far as expressing your disappointment that you would be unable to work for such a dynamic, innovative etcet person in such a market leading, etcet. company. Did you write accepting the post saying anything like "thank you for your letter of...."? and would the company have received it before you started work? Might be worth taking some legal advice, are you a member of a union or a professional body? Your local solicitors might give you a fixed fee interview to see what could be done. I would suggest you don't go to one of those no-win no fee ad type jobbies.