Advice about employing staff please!

Hello there, I actually have an accountant at the moment but I'm looking for a second opinion on this...

I run a small music agency. I am now at the stage where I'd like to expand, BUT as I only get paid when a concert happens, cashflow can be tricky. For this reason I'm not keen on employing someone 'properly'. I simply want to expand my business to make it look like a bigger entity, in order to have more 'punch' within the industry.

Many other talent agents in my industry have people working for them on a freelance basis. They simply work from home, and invoice the main company any commission they are due from concerts that they have booked (less a small admin fee for the infrastructure & privilege of using the name)

I would like to join forces with another agency, who currently already has their own list of bands. The other agent would be working under my company name, have his own email address @mycompanyname.com and appear to be part of my company from the outside. He would HOWEVER would carry on just as he has been doing for the last 3 years with his own bands, doing his own self assessment, working how and when he likes, and earning his own money. I would invoice him for a small monthly admin fee for the privilege of using the name and some of the infrastructure of my organisation.

Is this all above board in the eyes of HMRC?

I'm basically wondering if I can bring someone freelance (who currently does the job already) to work with my under my company name. Essentially we're talking about satellite individuals doing their own business and their own self assessment under one company name -mine.

many thanks, all very confusing!
Phil