Paying artists' expenses

I'm quite new to the arts sector and as FD of an arts centre I am finding that it appears to be industry practice for the arts centre to pay for what I would normally consider to be personal expenses for self-employed artists. I can find no source of authority to tell me if this is ok, or perhaps is ok but requiring some kind of return to HMRC? The kinds of payment I am referring to are for example physiotherapy costs for dancers, travel costs, subsistence/per diems, provision of meals and such like. As I write this list I just get an uncomfortable voice in my head that is whispering 'employee' to me and this worries me. Can anyone advise me or point me in the direction of some resource that will help me clarify this? Many thanks in advance.