Thanks to all for help and advice. I finally got through and solved my problem. It appears that the Heathrow Express Website does not e-mail "bar codes" anymore and simply sends a confirmation number (which I hadn't gotten, but did after I called in).

Also, the "345" sequence in a call to the UK from the US does not appear to work and jinx's the call.

Regardless, I now know the proper number to call the Heathrow Express and I'm grateful for the help.