IB and BA both operate widebody aircraft on this route as they are both owned by IAG and they both feed each others LHR and MAD hubs.
Correct - BA's current schedule is:
BA456/7 Days 12345 A320, Days 67 A319
BA458/9 Days 123567 A320, Day 4 A319
BA460/1 Days 12457 A320, Days 36 A319
BA462/3 Days 1234567 B763
BA464/5 Days 1235 B763 Days 47 A320, Day 6 A319
Equipment subject to change on the day, of course.