The time limit for suing someone for negligence is usually 6 years but if the problem caused by such negligence doesn't appear until later, then the clock starts ticking from the time at which the problem becomes apparent. (e.g. if someone developed an asbestos-related lung disease twenty years after working an a factory where asbestos was present, the 6-year period would start from when the disease first became apparent and not from the time when they were employed at the factory).
the other issue with the NHS is that adult medical notes only have to be retained for 10 years after the death of the patient or after the last treatment.
statutory compensation and no need to show negligence. Because of the legal nature of 'triggering' and along with the fact that it was so long ago and the firms may have gone under, you can sue for the whole lot against just one firm ( so long as it has money and handled asbestos) - very specialised area, and mostly form filling