I survey these today, with a dodgy GPS trace. There are 7 levels -3, -2, -1, G, 1, 2, 3. Level G is main entrance. Level 2 has access to Library, Malting Theatre, TK Max and toilets, with a foyer. All other levels just have access to the steps, three elevators and the car-park level. 
I've attempted to map level 2, but not other levels.