Ok, cheers for the input.
I suspected from the beginning that this was going to be the tricky part of the project
I did a quick search at Campoldy for the BB models mentioned by dbmtb
and all of them that they still have in stock are 111mm.
Then I checked the web page of Chicken Cycles and found that they have a lovely (and pricey) Specialites TA Italian BB (107mm length) that offers the possibility of fine adjusting chainline. As far as I can move it 2mm either right or left, I think this may be a possible solution to my problem.
The TA Specialites BB has almost the same price than a new Chorus BB.
Before taking the plunge, however, I will ask in a couple of long-established roadies bike shops we have in town to see what's their opinion.