In collective redundancy law, your “establishment” usually means your specific workplace, site, or business unit, not the whole company. Whether the 20+ employee threshold for collective consultation is met is normally judged against the numbers at your particular establishment, so an employer with several sites cannot avoid the duty by pointing to smaller numbers at each individual site while proposing large-scale redundancies overall.
If your employer runs five separate shops and proposes 25 redundancies at just one of them, that shop is likely its own "establishment", so the 20+ collective consultationCollective consultation is the legal process an employer must follow with employee representatives when proposing to make 20 or more people redundant at one establishment within 90 days. It is separat... threshold is met there even though the wider business employs far more people overall.