Has anyone come across this one...?

Whilst copying from a .csv file into an existing Excel workbook a
strange things happens...

The first column of my range loses its date format and changes from a
UK (the one I want) to a US format, peculiarly only on some cells!
Setting the format on the destination cells first first makes no
difference. I'm doing the copy in VBA using:

wkbSource.Sheets(1).UsedRange.Copy _
wkbTarget.Sheets("Timesheet Actuals").Range("A2")

Even more peculiarly, if I carry out the copy by hand the problem
doesn't occur...!

TIA

Jon C