I actually ached from shivering before the start more than I did afterwards.... it was pis$ing down ... take large flask of coffee, food for afterwards, towels, lots of warm clothes......sorry - i am probably putting you off here! We took a huge catering box of mince pies last time 
i would suggest (from experience) not wearing leggings (made me colder) and definitely wear wicking stuff - you see people with sodden cotton t-shirts that must be a so heavy and cold.
tested my Turbo-X shirt today in the pouring rain at lunchtime - was great - coudl wring it out afterwards - legs were just a little stiff though