I have a load of workbooks within which I need to change any cells
formatted with dollars to pounds. I have written this macro to do it:

Sub ChangeDollarsToPounds()

Dim Filename As String
Dim wb As Workbook
Dim ws As Worksheet

Filename = Dir("C:\Templates\*.xls")
Do While Filename < ""
Set wb = Workbooks.Open("C:\Templates\" & Filename)
Set ws = wb.Worksheets("Data")

Application.FindFormat.NumberFormat = "[$$-409]#,##0"
Application.ReplaceFormat.NumberFormat = "[$
£-809]#,##0" '**** code crashes here ****
ws.Cells.Replace What:="", Replacement:="", LookAt:=xlPart,
SearchOrder:= _
xlByRows, MatchCase:=False, SearchFormat:=True,
ReplaceFormat:=True

wb.Save
wb.Close

Filename = Dir()
Loop

End Sub

....however, the code always crashes with Error 1004 : Application or
Object defined error at the line shown. This code was lifted directly
from a recorded macro, but it seems that if I try to use it in any
workbooks other than the one it was recorded in it crashes at that
line.

I even tried copying the recorded code directly into a blank workbook
and running it and it also failed at the same place.

Any advice would be gratefully received...