Have you got access to a volt meter? If so, check battery voltage, If this is ok it obviously isnt your battery, So next step, put negatave probe of battery to frame or anything earth, Put the posative on the nut where the wire goes into starter motor and press the starter button (obviously with key on!) If you are getting a reading, then the wire is ok from the batt to the startor motor (and the solonoid is working as it should),
If no reading try the Solonoid (this is by battery under seat, its a small round thing, with 2 connectors on the top (10mm nuts i think) try crossing these with so