Batch remove all custom cell styles using VBA

Morning everyone,

I have a spreadsheet that I inherited from someone else which has at least 100 custom cell styles set. I want to be able to delete them all and tried to write a macro to do so

Sub Remove()
Dim cellst As Style
For Each cellst In ActiveWorkbook.Styles
      If cellst.BuiltIn = False 
Then
      cellst.Delete
      End If
Next
End Sub

While this got rid of some of the cell styles it does not remove them all. If i try and manually delete the ones that are there new ones just appear

Is there something else I can add to the code?

I have attached a blank copy of the workbook which shows the cell styles.

Thanks,

Alice