What has this got to do with stopping you, you may have no choice on the charity ride (good luck with it by the way), so its best to get used to riding in the rain, and wind as they are part of everyday British weather and it allows you to get more riding in, and its not usually that bad, wind you will get used to (perhaps not like, but develop techniques to lessen the impact it has on your riding), the avg wind speed I ride in is about 10mph over the course of a year.
to the thread, have a good read, it covers many topics.