Here is one way to replace all the currency format from one to another at one go.

Code:
Sub Sample()
        
    Developed By: ExcelFox.com
    
    Dim rngData As Range
    
    Set rngData = Range("A2:B10")
    
    Application.FindFormat.NumberFormat = "[$$-409]#,##0.00" 'Current Format
    Application.ReplaceFormat.NumberFormat = "[$£-809]#,##0.00" 'New Format
    
    rngData.Replace What:="", Replacement:="", LookAt:=xlWhole, SearchOrder:= _
            xlByRows, MatchCase:=False, SearchFormat:=True, ReplaceFormat:=True
End Sub
Works XL 2003 and above

Enjoy !