I remember going on holiday August 1990 from Stansted to Corfu on a Monday night with Air UK Leisure on one of their shinny new 734's. We checked in next to a Dan-Air flight, I think operating for Thomson Holidays going to Heraklion on the island of Crete.
1990 Stansted schedule has an Air UK Leisure flight to Palma on a Monday night at 2020, UK2115 for Intasun Dan Air 727-100 was DA2286 to Heraklion for Airtours Holidays departing at 2000.
Tour operator programmes could change very rapidly then as now, so I guess the UKL Palma flight was switched to cover a Corfu after the book I have was printed !