You can get a bracket for a zone one minidish to attach it to a pole
Last year the outside of the houses on my estate had rendering work done and when the scaffold went up 2 lads in a van come round, removed all the sky minidishes and fitted them with pole mounts to fix them to the outside of the scaffolding.
I'm not sure if you could get them the correct diameter for a drain pipe but it's got to be worth a shot
[EDIT]
Look in B&Q for large U bolts, see if you can make your own bracket