Still the Wayback Machine has copies of what they contained...
https://web.archive.org/web/20210409175919/https://www.bbc.co.uk/contact/death-duke-of-edinburgh-tv-coverage/
https://web.archive.org/web/20210409215827/https://www.bbc.co.uk/contact/complaints
Given the way the BBC responds to complaints in general, I'm not sure why people would bother.
The complaints from 2011 includes the following:
> Royal Wedding 2011, General coverage 09 May 2011
> Complaint
> We received complaints from members of our audience who feel that we devoted too much coverage
> to the wedding of Prince William and Miss Catherine Middleton.
>
> The BBC's Response
> The royal wedding was an event of national significance, which captured the public imagination both
> in the UK and internationally. We're pleased to have brought coverage of this celebration to audiences
> on the BBC. The fact that in the UK a peak audience of 20 million people watched the wedding
> service on the BBC and that more than 34 million viewers watched some of our coverage of the
> wedding across the day is testament to the considerable interest among our audience.
And:
> BBC News, coverage of Osama Bin Laden’s death. 04 May 2011
> Complaint
> We have received complaints from members of our audience who feel that we have devoted too
> much coverage to the announcement of the death of Osama Bin Laden.
>
> BBC News' response
> The discovery and death of Osama Bin Laden was by any standards a major news story. The
> operation to find him had lasted over a decade, during which time Al Qaeda has continued to mount
> attacks around the world. The details of his killing, his hiding place and the many political ramifications
> in the US, Pakistan and elsewhere fully justified the level of coverage BBC News devoted to the story.
They didn't give a shit then, and I doubt they'll give a shit now.