In my experience, international CLI is unrelable. On a few occasions, calls originated to the UK from here in FL will present some given London number as oppsed to INTERNATIONAL, UNAVAILABLE or something else. Occasionally they present as WITHHELD, even though I never surpress my number. Additionally, incoming calls from the UK may show a garbled attempt at CLI, for example, 441 is the NANP area code for Bermuda, so a call from, say +44 1234 567890 will show as HAMILTON 441-234-5678 or BERMUDA 441-234-5678 on my AT&T line. Sometimes the CLI will present with a generic number from a given city, eg ATLANTA, GA XXX-XXX-XXXX or NEW YORK, NY XXX-XXX-XXXX, which aslo presents on many calls made domestically from AT&T calling cards.

One other aspect to remember is that, from a UK perspective, the prfix 141 does not actually withhold the number; rather it is an instruction for the end/terminating equipment to surpress the calling number from being displayed on a subscriber's system - an important distinction. I vaguely recall in the early days of caller ID, there was a service based out of the Netherlands (I think it may have been called Xoip and had some form of callback function) that routinely ignored 141. Clearly a violation, but nevertheless it happened. I'm sure there were other examples.