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?

Presumably a bit of rubber sheet under the bracket should
spread the load and would be less likely to damage the render.

Havent tried it tho.

Maybe it would be better to have brackets with metal spikes on
the inside which would cut thru the render and hold on the brick.