this is what Corbyn was claiming was the NHS being sold off to The Americans.Not certain on this one but most of the UK pharmaceutical plants used to be R&D - they might be able to turn out a couple of kilos of active ingredient over a week long batch run. All quite small scale and focussed on providing novel compounds for clinical trials. That's what GSK's operations in Tonbridge and similar sites were doing when I was looking at a job there.
Most of the patented drugs were then manufactured elsewhere in much larger quantities in plants custom designed to produce a couple of specific drug molecules.
For a food analogy the UK research plants were Michelin starred kitchens turning out new and interesting things each week while the overseas manufacturing was a canned soup factory, making the same recipes over and over and over again for years at a time.
the NHS volumes are so huge, US pharma firms were offering to build bespoke plants to service NHS contracts if they got acess to NHS contract bids.