I don't know if this would help, but here's a couple of review videos of the Hornby versions of these coaches. The pipes you mention are vacuum pipes presumably for the braking;
https://www.google.com/url?sa=t&rct=j&q=...i=89978449
https://www.google.com/url?sa=t&rct=j&q=...i=89978449
https://www.google.com/url?sa=t&rct=j&q=...i=89978449
https://www.google.com/url?sa=t&rct=j&q=...i=89978449
Happily collecting things all my life...