Cooking kit and/or eating kit, depending on what food you bring. I'm guessing you haven't got a cooker, but you can probably beg/borrow use of someone elses. For cooking you can get away with a large mug and eat and cook everything in that, using a Spork for all mixing and eating duties, or you can have various degrees of cookware and plates, bowls, cups, cutlery etc. Again, I suspect you can borrow many things off of other people, but that may delay your eating if they are currently using them!
Waterproofs and/or clean & dry clothing, wrapped up in multiple plastic bags in case of major downpourage, which seems unlikely given the forecast, but there may be some light drizzle.
Torch and/or bike lights (depending on our efficiency and speed it may be getting dark by the time we get there).
Toiletries/Towel depending on how clean you want to be! (don't forget your toothbrush...)
