Thanks all for the comments.

The microcontroller that I’m planning to use is the PIC18F4550 that has onboard USB connectivity, for no particular reason other than having a few lying around at home. For me writing a full USB application is a daunting task, so instead I’ll experiment with the USB communications device class, which I’m already familiar with. This is equivalent to dealing with a serial port (1 MBit/s maximum though) and the required programming effort is minimal. It should be adequate to get the system working and I’ll look at full speed USB communication at a later stage.