How do I tighten up my Damixa Mekur single lever back to the sink ?

I have the 14000 (old) version of this tap which has come loose on the sink - Im able to strip the tap down from the top and can remove the ceramic mixer valve. But I dont know how to strip the rest. The diagram shows two bolts going from the top down but I cant see these bolt heads - Any suggestions. See diagram http://www.damixa.com/p/1143/Merkur/Kitchen-Mixer under technical information.