What expense category would paid website content fall under?

I run a number of information based websites which I sell advertising space on, and I purchase content for them from freelance writers in an ongoing fashion (articles/posts). For the first time I'm moving from needing to state a catch all one figure 'expenses' on a simple tax return to a full Self Assessment where there are more categories for expenses.

This is the only expense that I'm unsure of how to appropriately categorise. Is it best placed in 'other business expenses' or elsewhere (allowable expenses categories here ) I understand that this box is typically more often used for smaller expenses though I could of course explain more in 'additional information' .

The only other options would be 'advertising and business entertainment costs' (my thinking is that this is typically specific material to advertise a business, such as say newspaper ads and a promotional website - rather than the actual main website itself)  and 'phone, fax, and other office costs (but this seems too equipment and software based rather than actual content). Thoughts?