I have to say I don't know the answer to that. Perhaps Monsieur Roussel or Madam Lawson knows the answer to that.
Normally on the ballot, you would ask for an additional surname to identify the person, but on a special ballot, of course, that increases the risk of confusion and of the elector perhaps not knowing that additional surname. Again, that may be a good example, though rare, where the party affiliation would assist.
I'll take that under advisory. I would suspect that, in that case, the name with the combined party affiliation may be sufficient to identify the intention because the name is not incorrect in that case.