At least in your case the pulley has come off cleanly. You'll need to use the Sealey (SX400?) kit to remove the remaining internal sleeve piece, and get an INA pulley to replace this. As @Jellybean suggests above, this is considerably easier if the alternator is removed, and removing this is made considerably easier if you can get some penetrating fluid onto the two big bolts that hold it onto the casting bolted to the engine block (one of my bolts wasn't lubricated before trying to unbolt and snapped off inside). My pulley was so knackered that the end of the sleeve where you are supposed to insert the spline to hold it steady was rounded off and inaccessible to the tool. The mechanic ended up using a plasma cutter to chop the casing in half to get access to the removal bolts as it wasn't going anywhere with anything in my toolkit, and replaced with the 140A alternator I picked up on Ebay.