According to the timetable on their website the ATQ-BHX leg is codeshared with an airline which has ICAO code SGD. Not sure who that is (but can't help wondering if it's a typo, as SHD is Air Sahara...). I assume they would thus have the right to fly to the UK via the codeshare with the Indian carrier (as long as it has the rights to fly to the UK itself).