Cable routing around bottom bracket See picture attached of a point in the rear derallier cable routing - should I put something in there to prevent rubbing (I can't fit any brake or gear housing in there - so if so what should I use?), or is the cable fine going naked through the braze-on?  

Ditto for the other side and the front derallier, which goes through a series of curves and up into the derallier.

Thanks
You don't need to put anything in there. If you're really concerned get teflon coated cables. 

Those kinds of braze on cable guides were "standard" issue on well made lugged steel bikes until the early 80's or so. ( Cheap bikes came with bolt on versions of the same guides. ) They worked just fine even with old style cables that were much rougher than current cables. ( Current cables are pulled through a die to make them as round and smooth as possible and are also generally a much more rust resistant steel. )