Hello my friend,
I'm very sorry for not showing up here earlier, but the last days in the office had been very busy to say the least- plus I did a complete reinstall, because Mythtv was getting worse day by day.
Now that those things have been sorted, I tried the latest script from this thread and it worked :-) I now have incoming calls showing the proper callerid. The only thing I haven't tried yet, is making international calls from LMCE.
Thank you for your good job and I wish you a very happy new year!