According to the 1BWS publicity: "You can only use a 1bws ticket on those services starting or finishing in Wales and operating direct to Chester, Ellesmere Port or Whitchurch (Shropshire)." Does that mean you can (or should be able to) buy it from a driver in Chester, etc, or is only valid in the listed English places when travelling with a ticket already bought in Wales? (I'm guessing the latter as it talks only about services operation TO Chester etc.)