The Vigo flights were not available to book until June last year.
I tried to book in April and nothing was available, I contacted Iberia and they said that the flights would be available to book shortly. I eventually booked a return to Vigo in early June for a flight in late July and the load factor was about 80% outbound and about the same on the return.
I hope it returns this year, it is very convenient and the only link from England.