This goes down a storm with my mates and takes no time to make, obviously just leave out the prawns, replace with tofu, or even leave that out altogether, the packet of sauce is even on special in Waitrose at the moment.
I did this last year. Walked to the start and then caught a coach back into town with my family which was laid on by the organisers. Just to warn you it was total gridlock in that area! So the coach might be the most stress free option.