Windmill wrote:

From the street I can see a few cases where a TV mast has been strapped
to a chimney (the approved method AIUI) but, despite the metal corner
brackets between the strap cable and the chimney, the render has been
cracked at the chimney corners and has separated from the underlying
brick.

Is there any way to make this less likely, given that a cable would
probably need to be under a fair amount of tension to hold a satellite
dish firmly in place?

Use of the brackets that uses packing strap instead of lashing wire?

http://www.blake-uk.com/stackstrap.aspx

Although I notice they now sell plastic corners for use with it, which
weren't available when I put mine up.