Giles you may well be correct.
Wizz i believe do have two A320s due for delivery in the first quater of this year so they may well go straight to the BUD base.
Think its unlikely they will change the LTN based summer a/c that does Split , Dubrovnik and one new route ( 06.00am early morning depts) although as previously said Dubrovnik still isnt bookable so they are holding back for something.
FR will be doing 2x Daily BUD-STN most days as well.
I feel sure Easy would have looked at the opportunities.
Looks like north of London is going to be saturated with flights to the Hungarian capital