At Waypoint 1 you will find a set of coordinates for Stage 2. This will be somewhere in Southern England. Once you have these coordinates track down a cacher who lives in the area. Explain what you are doing and ask them to go to the coordinates you have and retrieve the coordinates of the final cache. When you are given the final coordinates go there and sign the log.
Try to find different cachers to help you rather than those who have already found the final cache, although there is no rule against this.
There will be another similar cache working in the opposite direction so don't be surprised if you are contacted by someone asking for help with their Stage 2. If interested in the partner cache it is GC69njj.