As i mentioned in postings about the 32" Avant tube replacement i was going to try to find an affordable replacement for the 28" 100Hz Avant.
Just now i did the first replacement with a non-B&O supplied tube: the original W66ESF002X44 is replaced by a W66ESF012X44 which seems to work fine.
However, this new tube has a manufacturing date of 2004 on it (supplied in 2009 !!) and was still made in France, so it seems suppliers sell nos parts.
The good part though is that it's around 200 euros and easy to replace, even the connections are the same as the original tube (with the 32" replacement it still needs changing of connections for deflection).
So, also for the 28" Avant there seems to be a reasonable solution around (while stock lasts ??), bear in mind that the tv will be as good as new with a new tube !!
Btw thanks to Maarten B and others on CO forum in NL.