This could go some way to help justify why First North Western didn't see fit to make further alteration to the class 156 fleet whilst under their franchise term. A mere 8 years after initially being attended to could've seemed like unjustifiably unnecessary expense.
http://dysgraphyk.madasafish.com/156/class156nw.htm
http://dysgraphyk.madasafish.com/156/class156nw.htm