I have put the code you suggested in at the end of my checkout/end.php file as shown in the first screen shot in the attached file. I was using the / banktransfer_end.php but it didn't show up in the source code view of the thank you page so I reread a post pointing me to the end.php file.
However I when I do a purchase using check as a payment I am brought to a page shown in the second screen shot in the attached file.
The source code is shown in the 3rd screen shot in the attached file.
It seems to mess up the check out process.