I agree with previous posts, it shouldn't really be necessary. The average body will hold around 2000 calories without carb-loading and doubt you'll use more than 1500 calories to get round a Half

Carb-loading done properly over 3-5 days will only give you another 800 calories or so on board. You shouldn't need gels for a Half either - before you go down that route! Although some peeps do benefit mentally from them - the same way as a pair of lucky socks can help others

Enjoy your Race, Simon and it wasn't a dumb question.