OK, sorry, didn't know about that.
I think the ACToolbar shouldn't be added as a control in the Design view as otherwise I can't declare the control in Sub Globals().
So now I have:
B4X:
Sub Globals()
Dim edtID, edtFullName, edtPostcode, edtGP As EditText
Dim btnFirst, btnLast, btnFind, btnShowNext, btnPrevious, btnNext As Button
Dim lblRowCount As Label
Dim ACToolBarDark1 As ACToolBarDark
End Sub
Sub Activity_Create(FirstTime As Boolean)
ACToolBarDark1.Initialize("ACToolBar")
ACToolBarDark1.LogoBitmap = LoadBitmap(File.DirAssets, "Test.png")
'etc. etc.
End Sub