Probably be something soft like 'Last Waltz' by Englebert.

What would be a fitting tune?

I think they are going to do what they did last Saturday.

We are the champions.

He is a champion - a charming gentleman; she is a champion - a charming lady.

He should not be allowed to leave.

They mentioned Murder on the Dancefloor on ITT.

I hope they do the routine they were gonna to "Murder on the Dancefloor"

From their interview on ITT, I understood they are doing their waltz from the first week.
Though I do wish it was 'Murder on the dance floor' with live ammo.