I'd like to hear your evidence for this. If they weren't "fit for purpose", they wouldn't be running. Yet, they are, and the services the run still carry large amounts of passengers. I should know - I'm a regular commuter on them.
Yes, they're not the most comfortable but then again I can only think of one or two classes that are more comfortable. I can also speak for their reliability, at least from my own experiences. Where other units have failed (maybe a 334 thanks to snow or a 170 because of a gust of wind) the 156s have pretty much always shown up.
I'm sorry, but just because they're not your precious 37s doesn't mean they're not fit for purpose. They obviously are, and indeed operate some pretty important commuter routes in Glasgow.
Well firstly I have never mentioned class 37s in any post of mine since joining this forum, so try again on that score!
Why are the S/R 156s not fit for purpose?
Take the seats shall we - despite many many changes of cover, the bits that matter ie the sprung seat squab (cushion that you seat on) and the associated backrest are in most cases the original fittings. The squabs are variously lumpy, have metal framing with no padding left around it or no wadding over the springs. The backrest internal filling's have shrunk to the degree that most if not all seats have a gap at the top between the backrest and seat frame. The armrests are often missing or so droopy as to be useless.
To move on to ventilation. Because they have no forced air ventilation or air con, hopper type windows are fitted. Many of these won't stay shut when passing another train or entering/exiting a tunnel. When open these hoppers create a significant draught, not for the person that opened them, but for the unfortunate sitting on the opposite side one or more rows back.
The heating system is either on or off, and in winter owing to relying on an old fashioned coolant heated from, and piped from the engine, cannot keep the train warm, let alone hot.
Turning to the rest of the interior, many vestibule doors are either missing or jammed open. Rubber door seals are worn and have gaps allowing draughts to arise. As there is no heating in the vestibule the cold air then enters the seating area so those passengers near the vestibules lose the benefit of what warmth there was.
Finally the toilets - still emptying on the track in 2011!
Just because they are reliable (no dispute there), and carry large amounts of commuters (who have no alternative) does not make them fit for purpose.
My evidence comes from regular use on the Stranraer-Ayr and Carlisle- Glasgow GSW services.