It's most likely not a BECM problem to start with.
The windows switchpacks are known for failing randomly where they will just not move any of the windows.
Do the rear windows still work from the door controls? If so, then I'd suspect the window switchpack before anything else.
As PPP38Vogue says - I do some BECM work, can do unlocking and basic repairs - but I also have looking into the window switchpacks to try and find out why they fail, and now offer repaired ones on exchange for the faulty one. I am away working with my day job, pretty much until the end of June, so not a lot of use to you at the moment though!
There are a few common areas where they fail, and 99% of the time they are repairable - If it was just a single switch that was faulty, then they are easier to do, and I did a writeup on how to fix the switches. But a complete failure of the switchpack is a bit more tricky to locate sometimes, and generally require some fiddly work around components to repair broken tracks.
Check the rear door window switches, as the BECM drives them directly. If they work, then chances are the window switchpack is faulty. If they don't work either, then it's either failed with the rear window switch inhibit on, or it is an internal BECM problem - but I wouldn't be ripping it all out just yet. If it's the switchpack, then it's generally a 10 minute job to replace the faulty one, once you have the replacement.
If it is the switchpack, then I'd be interested in buying the faulty one off you to add to my pile of ones to repair when I get home.
Marty