Work disciplinary procedure?

ive been suspended pending a full investigation from my job. there are 6 allegations against me, i have had an initial meeting with my area manager to give my version of events. i was sent a letter asking me to go to a disciplinary meeting, the letter states that they have attached all the evidence they have collected against me, but the only thing attached is the minutes from my initial meeting with my area manager. are they allowed to hold back evidence until the meeting? if so what do i do when i get there and they show me the proof that they have,,,if they have any? and also, what do i do if they don't have any (as far as im aware they haven't spoken to any of my colleagues, even though a couple of them could have backed up my side of the story)