I'm currently refurbishing an old Hornby Cl 110 dmu, replacing the old Ringfield motor with a Black Beetle unit, and the couplings with nem pockets in order to use a fixed bar for closer coupling. My problem is with the type of plastic used on both the nem pocket and the Hornby bogie. I've tried sticking them with Evostik, Araldite, superglues, plastic weld and Draper's hard plastic adhesive, the one used for joining plastic pipes. None of them can withstand the hook and bar being pulled out, without the bond breaking. I've cleaned the surfaces meticulously each time there's been a failure before trying a different glue. Does anyone have any ideas what might overcome this adhesion problem? I could just use a hook and bar, and might still have to, but I would prefer to keep to the nem coupling if possible. Thanks.

I think it is a type of Delrin & if so, almost imposible to glue for strength.
In thses cases, I would  mount the NEM pocket direct to the body/chasis as the normal practice on USA models. Even long Proto 1000 Budd cars for H0 has the coupler pocket mounted on the chassis & they go around 18" curves.

Thanks Sol. In the meantime I've welded the parts together using a soldering iron and similar plastic melted against the two surfaces. Seems to be holding okay though it took a few melted nem pockets before I got the hang of it.