Best is simply to use BA’s webform. When selecting claims for delay you can pick EU compensation and add any ancillary expenses if it was not covered by BA already. The form does not let you add further complaints and I feel it is the most efficient way - why bother wasting your time ranting while the compensation for a technical delay will be all the same.

Here is the link: https://www.britishairways.com/trave...evice-mobile#/