Advice Needed!

Hello All!

I'm new to the forums and wanted to ask for some of your opinion/advice:

I'm doing a Photoshop Website Mockup for a client from another country (this is the first time I've worked with them). The design has been signed off and I just need to send them the photoshop files. I sent them my invoice last week along with the final screen proof. (I didn't ask for a downpayment at the start of the project)

I haven't received a cheque from them yet, but they are asking for the photoshop files already. Should I send it to them, or wait until my cheque comes in the mail?

Thanks for you help!