Removing an older vanity basin:
Now if you have removed the bath and you are also removing an older basin then now is the time to do so. Simply remove the basin vanity trap same as you did the bath. Either unscrewing all of it or unscrewing and cutting off the waste pipe or removing the waste pipe altogether if you will not be reusing it.
Next go under the basin and undo the nuts where the tap ware pipes come out of the wall. Or if there are no nuts use a hacksaw.