Arrival time is what counts for UK/EU261 delay compensation purposes, and your flight arrived quite a bit under the 3 hours short haul threshold (the scheduled arrival time was 18:55).

However, as your flight left more than 2 hours late the "right to care" (food, drink, roaming costs etc.) was engaged and you'd be entitled to claim back any reasonable expenses you incurred in this respect.

Of course your claim should be directed to EI as the operating carrier - BA5976 is just a codeshare flight number.