The Right Way to do an Eightfiggie?

"Where am I?" How to get an accurate
eight figure NGR from this? (Wikipedia)

Responsible metal detecting means taking responsibility for recording the details of the context of discovery of an archaeological find removed from a site or assemblage and reporting it. I was discussing the indications that the PAS is intending to take a stand against sloppy recording by finders, and the discussion surrounding it. There was a revealing comment in that thread, Owain 1405 wrote (Wed Jan 08, 2014 12:13 pm)

Wouldn't have thought the 6 figure grid references are that accurate anyway. 99 % of finders wouldn't be able to give that sort of accuracy. Suspect they would be shown a map and point to rough area where find came from and then PAS give GR to best of their ability. As for insisting on 6 figures GR's, can't see that happening as the whole point of PAS is to encourage the recording of finds, make it too complicated and your average joe public wouldn't bother with it.

So the finder points by memory to where they found something and the NGR is then supplied by the FLO? In other words, basically no reliability whatsoever because there is no way to verify it at all. It's rather disturbing to read that the average detectorist would in any case fiond giving even a six-figure NGR "too complicated". Of what reliability are the "data" which they are reporting to the PAS recorders? Just before the thread was deleted by the forum owners (and I regret I did not download it) a member was giving an account of producing an eight figure NGR by standing in the middle of the field and looking where the findspot was in relation to distant features like a church spire and trees, and then back home, fining such a spot on the map. Obviously an eiyght-figure NGR of a particular point on such a basis has absolutely no value as a record of the information lost by the removal of that object - as the people who deleted the thread apparently realise.

What actually lies behind the locations given on the PAS database? In what way is this information verified by the PAS?