Individual doctors don't make purchasing decisions, but they do make prescribing decisions which drive sales. They are the key stakeholder when it comes to pharmaceutical marketing. They may not be buying lunches in the UK, but sale reps are getting time with doctors and talking up their products.
BTW, is there a law in UK (or US) about using generic products? Over here, a doctor prescribes something, but pharmacies have the responsibility to offer cheapest product, typically a generic replacement when available, unless the doctor justifies a specific brand with specific medical reasons (which are rather hard to come by).
Individual doctors don't make purchasing decisions, but they do make prescribing decisions which drive sales. They are the key stakeholder when it comes to pharmaceutical marketing. They may not be buying lunches in the UK, but sale reps are getting time with doctors and talking up their products.