At what point does the free supply of a product (P category) to a physician in the UK become a clinical trial in which the company providing the product becomes the sponsor?

Companies are not infrequently asked to provide products free of charge to physicians who are either interested in gaining experience with the product or planning to include it in their own research. I am looking for guidance on where the boundary between the supply of free product and the company being seen as the sponsor of any subsequent research might fall? In some cases the company might also be asked to provide some additional support such as one or more of the following:
- grant to support the planned research
- input into approriate research design
- support to analyse data
- support to write a publication

Does anyone have an opinion on when the company should consider themselves to be the study sponsor rather than simply meeting a request for free product?