How to say no politely to customers/clients?

• biology course online
• choice university online

My friend and I sent emails out to bands saying that we are happy to produce a free music video for them as part of our University course. However we only need to do two videos, and only have the time to do two and the problem is that more than two have said yes.


So how do I politely say no to clients we have personally invited to help them?


After this year I will moving back south so I won't even be local once those two videos are done.

How to say no politely to customers/clients?