Thanks for the comments, guys.
Zharin - that's a very good point, and not one that I believe we've considered. To answer your question, we have always received support for BES from our carriers (to date we have had two). It is the carrier who escalate support incidents for BES to RIM if necessary. Without looking into it I wonder whether this situation is country-specific; will RIM support BES for UK-based companies? Just wondering whether this might be why we have never been offered direct support as a possibility. I will certainly investigate this...
voiceBerry - unfortunately all the talking that can be done has been. If we insist on doing this upgrade ourselves, our support for BES will be suspended indefinitely. If we were to perform the upgrade then call the carrier for support (even some months down the line where the problem may not even be upgrade related), the carrier would insist on sending a Techie out to "repair" the server whatever the fault (obviously faulty because a monkey - me - performed the previous upgrade!</sarcasm>) Our support would then allegedly return to normal. It seems we can't get away from having a Techie out one way or another. The whole situation really is quite unsatisfactory