Hi Matt, I've got my TRA skills assessment for a chef too. Mine came through in February.
In terms of what you need, I needed all my pay slips an p60's of the last 5 years. You need references from all your places if work, these are quite in depth, requiring you to list all the jobs you do regularly. You need all the paperwork you have from college. Certificates and reports. It's a difficult process but if you need help just let me know!
Feel free to message me and I'll send you some of my copies of what I sent.
Good luck
Joe