JFZ90, to try and answer all of them:
Are the numerical definitons of tolerable and broadly acceptable in relation to Nimrod safety known?
This should be available to those who have the safety case.
I assume "broadly acceptable" (at system/aircraft level) is up around the 10-7 / 10-8 failures (with critical safety consequences - i.e. loss of life/serious injury) per (flight) hour, but where is "tolerable" risk zone - 10-5, 10-6? I assume these numerical definitions have been set by the Nimrod project, based on extant HSE guidance & other project comparators?
Military Airworthiness requirements are in JSP 553, Civil requirements are in Certification Specifications (eg CS.25). They represent single figure numerical targets rather than "zones"
Can anyone point to some example HSE type rates for different types of system/project (e.g. airliners/oil production platforms etc.)?
The HSE guidance is based on risks to people, rather than about different technologies / industries. However, it does have some interesting stats about various activities.
sw