I am very surprised by some comments regarding actual circumstances of maintenance activities being 'difficult' eg it's dark, cold, stressful, etc. and potential 'knee-jerk' reactions and 'time consuming' changes to procedures in response to whatever exactly happened.
Hello? We're talking about 75 passengers and crew flying over the heavily built-up capital of the UK.
They were very lucky that the cowls separated when they did without damaging the airframe. Given the starboard engine fire, can you imagine the consequences of the flight having been unable to make it back to LHR coming down anywhere along the approach to LHR?