Lightweight Top:  Although the temperatures during the day can get up to 48 degres (ouch that is warm), at night it can get really cold.  I can't lug fleeces around because of the weight, so the majoity of runners opt for high quality lightweight (less than 100g) tops.  These are put on at the checkpoints.  They are also used during the 50 miles stage which goes on well into the night.  They need to be high quality so that they breathe and keep you warm at the same time.  I have found a couple by a company called Montane but there are others.  Quite a few suppliers and Alexandra sports in Portsmouth have very kindly provided one at a discounted rate.