Gums, I found the original thread way down the page.
Anyway, based on 'anything' we used to have a 14% minimum landing fuel on one type during training which was reduced to 11% once qualified on type. Operational limits were just half that overhead but for practicable purposes I think 9% for wife and kids. Sometime later the fleet minimum was increased to 14%.
Diversion fuel OTOH was always interesting with the basic instruments to visual and climb out and transit on top. UK may have had lots of landing surfaces and in emergency the Harrier is best placed, but where open runways are concerned things can get very dark after 5pm. In worst case, landing short at the diversion or overflying a red/Amber base for a blue diversion may be a sensible option.
orca, you will remember the emergency landing on a Spainish Mership, what happened there? Had mother moved?