4.2 Can I cross-match my own list of positions with a VizieR catalogue ?

Yes. Use the Tables management tab on the cross-match web page to upload your own table.
Currently, we support VOTable, FITS table and CSV as the table input format. If your table is in another format, we suggest using TOPCAT to convert it to VOTable.
Here is an example of a simple table you can upload :

RA,DEC
2.514167,+46.39083
4.107500,+53.945278
4.172083,+54.660556
4.626250,+26.139167
7.465000,+38.324167
9.805417,+3.134167
10.665417,+71.366944
233.190417,+68.866667
113.448750,+52.689444