With some help on an electronics forum and just running the risc i've found an affordable alternative CRT (also Philips made in Czech republic) sold for around EUR 250,- to the B&O ''solution'' (price of a CRT EUR 700,- therefore not worth it).
A replacement tube for the W76ESF331X44 is the W76ESF021X44/L, but the problems to overcome:
-connections of deflection coils are different, so either solder the wires direct to the connections or replace the little connection board on the tube with the old one (which is what i did).
-Earth field correction coil from the old tube fits on the new one, but the small pcb on the tube neck not since the new tube neck is thinner, i filled it up with some soft material (preferrably low- or inflammable).
-After making the (usual after every tube replacement) necessary re-adjustments the result is really great: these ''cheap'' tubes seem fine: good convergence and geometrie, so ''powered'' by the Avant electronics i doubt if one could see the difference with a B&O selected type.
So your 32"' Avant now doesn't have to go into the ''bin'' anymore, mine is as new !!! :).
I'm still checking for a similar replacement for the 28" Avant because i feel on one hand finding an affordable replacement is good for keeping the Avants going for many people (one of the few tv sets worthwhile spending some money on these days) but on the other hand the solution offered by B&O is never worth it because of the prices they charge for replacement tubes.
Hope B&O can forgive me for trying to prevent older Avants being scrapped because of this, after all they were made for 20 years and not for the average 10 they seem to last....:)