I thought the Coroner's verdict was a narrative verdict.
The most interesting line from the inquest report was that he wouldn't have locked himself in the bag unassisted without taking a knife, as he was "a risk assessor".
Looking at all the evidence, my opinion is that he was murdered, and it was made to look like he killed himself. Whether MI6 either as on organisation, or individuals within MI6 were responsible, who knows, but I would guess that they were, based on how well the scene was cleansed for DNA, the attempts to make Gareth out to be a bondage and drag queen weirdo, and how long it took for him to be reporting missing by MI6.
The Coroner rightly says we will probably never know how Gareth died. I have no doubt whatsoever that there are government agencies in this country which in very exceptional circumstanes, bump people off.