Hello,
Many MBA adcoms do offer the option of
Skype interviews for people who are not conveniently located near a city where they are interviewing in person. That said, many applicants do travel 100+ miles more for interviews (you said more than 100 -- so 105 wouldn't be a huge distance away, but 400 miles would!). If your schedule permits you to interview in person in London, I suggest doing so, as making the effort will show your commitment and enhance your positive impression. If it’s a huge burden, it is fine to ask for a Skype interview. Each school will have its own criteria for Skype, including time frames. You would have to check school by school to see if they do it on weekends.