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mostly buried my head in the sand.
I found a few areas where the ants were actually coming in and out (rather than just pushing insulation through gaps. So i put poison down around those areas and sealed up everywhere else. It seams to have worked - but could just be they died out over winter, and are planning a come back?
The alternative of taking all the internal walls off, and redoing everything is not something i fancy…
i've had something that looks similar, it was ants.