If it costs you more to get to work than you get paid that is not the employers problem.
If employer offered London weighting then the commute to work would not be as expensive, so london weighting could be an argument of T&C e.g. crew who are Manchester based should they be on same Basic as crew who are London Based ? It's just another for the melting pot.
Not a pop at Manchester crew just an alternate view point for Grease 7