BA has confirmed the summer regional routes in a media release:
British Airways - EVEN MORE REGIONAL FLIGHTS TO HOLIDAY HOTSPOTS NEXT SUMMER
From May 2018 there will be extra weekend flights from Manchester to Malaga, Ibiza and Palma, with Mykonos flights operating on Saturdays instead of Fridays, an extra weekend flight from Birmingham to Palma and an extra weekend flight from Bristol to Malaga.
Additional summer routes include flights from Manchester to Alicante and Nice, from Birmingham to Malaga and Florence and from Bristol to Ibiza, Palma and Florence.