Voluntary returns from UK

[Worriedworried]

Hi.... thanks in advance... any advice is appreciated.
My partner is returning to Albania after being here illegally for 8 months. No passport, is lost, but has a photo copy of passport. I have booked him a flight for 6 weeks time. We are going to fill in the Voluntary departure form but just wanted to know:

1) the process
2) how will the travel document be issued
3) will he have to go to any interviews?

Any previous experience of this would be great
Thank you