Sorry, I might not have been very clear.
One of the routes form Three Bridges to Newport is LONDON. So I'm think I can use:
Three Bridges -> London: LB, LB+SL, SC
London -> Newport: BD+MW+WX, LA, LA+SB, LW, LW+WX, WE+WX, WR
Hence my route of LB+WX+MW+BD
And thanks to collybs, I...