The1975 are subbing Lana on the 18th in Portugal and that’s only a short distance from Spain so I expect that pairing to be repeated at Beni on the Friday.
Franz Ferdinand playing at a Norwegian festival on the Thursday and supporting KOL in their UK gigs, so wouldn’t surprise me if they are the Saturday sub.
Fatboy, George Ezra and Jess Glynne don’t seem to have any other commitments on any of the days but worth noting that Ezra/Fatboy share the bill on one of the days at IOW so I wonder if it might be the same here (except Ezra is headlining IOW with a Fatboy closing set, whereas Fatboy is headlining Beni, potentially subbed by Ezra). If this pairing is kept together it could either be Thursday or Sunday.
Kodaline playing a festival in France on the Saturday and Germany on the Sunday so have to be on one of the first two days (possibly Thursday would be the likelier of the two since Lana Del Rey and presumably The 1975 are both Friday)
If Kodaline are the Thursday sub then that probably means the Fatboy/Ezra pairing is more likely to be Sunday.
So my best guess is that we’ve still got a Thursday headliner to come who will be subheadlined by Kodaline, with The 1975/LDR, Franz/Kings and Ezra/Fatboy being the other three pairings, in that order.
That leaves Jess Glynne who could fit in as the third down act on any of the four days.