There is no such thing in the UK or Europe as a licenced airworthiness engineer.
The term isn't used elsewhere that I'm aware of, but the concept would describe a DER - Designated Engineering Representative in FAAland. It's very useful there, but of absolutely no value here.
The nearest equivalent in JAAland, or the UK defence industry is the concept of a "design signatory" - there is no formal qualification as such, although pretty much anybody in this role will have either a good engineering degree, or a maintenance licence +plus shedloads of experience. A design signatory is somebody who has authority to sign for certain functions within their employer's approvals.
Becoming a design signatory within a company comes with a senior engineering job, and isn't a separate licence. The overseeing organisation that gives this status will do so on recommendation of the company, and will take into account the total experience of the person being put forward. ATPL passes and flying experience will certainly count towards that, but are no substitute for a top-notch combination of engineering experience and technical/academic qualifications in engineering.
I've been design signatory for several CAA approved companies, although don't currently work in that capacity. It leads to a deeply suspicious nature and obsessive attention to detail.
If you've not done so already, what you probably should do in your current position is pursue CEng or IEng status through the RAeS, which will carry a lot of weight in pursuing such senior positions.
G