Interestingly, the One World website timetable search shows that there are 6 departures during this period:

14:20-15:35
14:55-16:20
15:00-16:20
15:55-17:20
16:30-17:50
16:50-18:05

It would therefore seem that all of the flights showing on both websites combined are real flights - quite surprising that there are 6 MAD-LHR departures within that period and 2 of them are within 5 mins of each other!

What also seems strange is how the 2 IB operated flights which appear in the BA results, do not appear on IB's own website.