Thanks Jim. The SECR Birdcage coaches are the Bachmann RTR ones just straight out the box. I quite liked the look of them but I've been struggling to find an excuse to run them. I thought perhaps a travelling theatre company special. I've seen photographs of such trains on the Midland and LNWR which included CCTs and open carriage trucks along with the coaches. The LNWR train pictured at Colwyn Bay included CR stock so some of them must have travelled a fair distance. Not sure if the birdcage would be within the CR loading gauge though.
How to do it, advice sought and offered.