the architectural orthodoxy seems to be that new additions/extensions/adaptations MUST be in a strikingly different design to what was their before so that the original architecture is not compromised by blending something new in with the old. (ie so you can see what is new and what is old)
That's an interesting point. There is something to be said for making clear which parts are original, but I've yet to see it done in a way that is sympathetic to the original structures. Therefore, I think I would in many cases tend towards recording any alterations in great detail so that interested parties could find out what is original and then building in a similar style to the original. Perhaps new parts built to the same style but with slightly different materials would work; at Shrewsbury I seem to recall that an alternative design for
the new waiting room at Shrewbury (not my pic) would have used blue bricks, which may or may not have worked with the red brick of the existing station (what they ended up building certainly doesn't seem to work from the photos I've managed to find, although I've not seen it in person). In that case I objected to the new waiting room planned not just on the grounds of aesthetics but also because it appeared to offer less space than
the previous one (again not my pic), which itself wasn't big enough, and would be draughty with pepole using the lift and walking through the waiting room to reach the platform. The old Shrewsbury waiting room shows another way of building something (presumably) non-original and making it stand out from the original buidling. The colour doesn't work, but I think if that had been a dark, varnished, wood it may have looked in-keeping and yet still have been distingishable from the rest of the station.
