My advice would be to read up on this and claim.
The legal position, explained to those who have a duty of care, is that as soon as a technical solution becomes available, the clock runs on litigation. There is a brief period of grace while the project is approved. If the MoD wants to seek a waiver from the legislation, the Secretary of State must sign it. I’ve never seen one, although one may exist. The intent of the legislation is such that waivers are temporary and to meet an urgent requirement.
For aircrew who wear helmets (as opposed to headsets), the clock began running in 1997. After that date, MoD haven’t a leg to stand on. To be fair to OR branches in London, on 25.8.98 they sought advice on how to initiate a Tri-Service aircrew hearing protection project (the idea was to establish an IPT). However, the reply from MoD(PE), dated 1.9.98 and in the form of a Board Submission seeking the funding to kick off the programme, was buried as there was too much opposition from on high.
I mention this because, if pursued, MoD are likely to claim the clock runs from issue of the Defence Technology Strategy (2007, page 129). Even then, when asked at the time, the Centre said the DTS was only an initial acknowledgement there may be a problem; which was disingenuous given the technical solution (at 85dB(A)) had been in service for 11 years and upgraded to meet new legislation (75dB(A)) in 2001. As a result of the DTS, the Nimrod IPT (for example) issued an ITT in 2007 to conduct a Research and Development contract into the concept, with an aim of achieving 85dB(A). When one bidder pointed out the spec they were seeking had been obsolete since 2001, and a better solution was actually in service, the MD was bollocked and the company effectively blackballed. That’s what you’re up against.
Best of luck. If you want the ANY of the above evidence, PM me.