For GWR/BR(W) modelers, and more recently GNR/LNER/BR(E) modelers Timbertracks supply an excellent range of lasercut and lost wax components including valences, canopy supports and
Columns. There's also chimneys and drainage pipe details too should you need those too!
It's also worth looking at the scalelink range too (already mentioned)
Here are the links:
http://www.timbertracks.co.uk/index.php?route=product/category&path=5_6
http://www.scalelink.co.uk/acatalog/index.html