I have been asked by our HR dept to create a plan for dealing with a workplace fatality which, hopefully, we will never have to use. I am OK with the reporting requirements, and I have a copy of the National Liaison Committee Protocol to work with but I thought I would ask if anyone has had any experience of dealing with such a scenario and if so what learnings were there?
Any help would be gratefully received.

Thanks ray if you could find it that sounds like it would be extremely useful. If you don't mind sharing it please PM me for my details

Couple of thoughts from previous employments:

The presence of immediate blood family / marriage relatives within the workforce at site at the time of the incident - pervious employment we had a father, son, brother and nephew on the same shift (albeit in different parts of the factory) and a non fatal accident to one disrupted operations across the whole site. So there is a need to control information dissemination internally as well as externally.

Then there is the scourge of "dumb phones" placing an incident in the public domain via social media before your designated manager is even aware something has happened. Such "news" releases choke vital communications lines when the world and his wife ring up enquiring as to what has happened. Was so much easier to control when the outside world required a fixed line / pay phone for communications.

And if you have them, the sensitivity of gate personnel / security guards, when and if the media and relatives arrive at site. These personnel even though a sub-contractor were included in our emergency procedures training.

Add to the previous good advice, there will be longer term affects:

grieving work colleagues will be absent, resign or achieve very low levels of productivity.
Expect to lose much production time.
Be prepared for the Coroners Court (if not obviously natural causes)
Ditto Magistrates/Crown Courts
A major on the Annual accounts

You might also want to look at the protocol from the HSE
http://www.hse.gov.uk/enforce/wrdp/

"The presence of immediate blood family / marriage relatives within the workforce at site at the time of the incident - pervious employment we had a father, son, brother and nephew on the same shift (albeit in different parts of the factory) and a non fatal accident to one disrupted operations across the whole site. So there is a need to control information dissemination internally as well as external"

Short of physically restricting verbal communication, and possession of communication devices, that will not be possible. Given that locally family members are electronically communicating between each other in real-time, using instant comm apps like whatsapp.
Then we come to the moral problems, since you seem to be suggesting that nearby employed relatives should not be informed?

There's nothing in your protocol about contacting family, unless you are including it under "reporting".

A friend received a call from his wife's workplace. Unable to make sense of it he asked what they were talking about, and got the reply "Oh, haven't the police told you that she's died?"

In addition to the previous posts, you may also find helpful advice in the IOSH Guide 'Learning the lessons', which was developed specifically with fatalities in mind.

JohnMurray - The OP asked for experiences and as such the suggestion was that any plan needs to consider how to inform family members working at the site at the time of the incident - not that they should not be informed.

A planned approach is required as for example (as happened) a work colleague mentions the incident in passing a remote work station and a distraught family member rushes to the scene leaving plant and machinery in operation unattended with the potential to injure others as well as resulting in significant business disruption. Part of our adaptation plan post this particular incident was to ensure we had "up-skill" operatives developed in each area so that if an employee urgently needed to vacate their position any operations would not be left in an unsafe manner but had someone who could at a minimum safely stop equipment in a controlled manner.

On the issue of personal mobile devices on the shop floor the majority of my employments consider this a disciplinary offence (with riders for expectant fathers, relative carers i.e. what the moral majority would consider exceptional circumstances and then for incoming phone calls only) so it has not been an issue with social media other than when line supervisors have turned a blind eye for an easy life.

Should site Risk Assessments nd training consider operatives using social media whilst executing their employment duties? are they actually performing their obligatory contractual activity whilst engaged on personal electronic communication? - probably a separate discussion thread already flogged to death in other posts in respect of company drivers and those driving for work.