If the blisters are on a pressure point they will just increase in size, becoming more painful, until they burst of their own accord. There is more danger of infection from this as dirt will probably get ground into the raw area. To burst safely I carry a small bottle of surgical spirit and a large needle. Wipe blister and needle with spirit. Allow both to dry as the spirit stings. Pierce blister in two place then gently expel liquid. Pat dry and cover with blister plaster - Compeed is my choice. It is possible to make a protective ring around the blister using plasters, but this can be quite fiddly. The real hard core treatment used on some desert marathons is to inject iodine solution straight into the blister. Excrutiating but reported to be effective.
Might be completely wrong but I have a feeling that it all went a bit sour when they stopped selecting the Forum 6 to run London. Unfortunately there was such a high instance of injury (up to 4 being on the bench at any point due to unrealistic training plans that) London became a bit of an embarassment. Cynical Bear thinks they switched to Paris as they knew that this would generate less interest and scrutiny from the forumites. Although they still use London to sell their magazine their involvement has since then markedly decreased.