Thanks once again, FP.
I'll probably take the replacement LNB route. As the dish is at head height on the bungalow wall, it won't have to be a death defying stunt at the top of a ladder. (For this relief much thanks!)
I think that a like for like swap of the LNB is likely to be the best bet.
I don't want to change the alignment of the dish or replace the LNB with a different piece of kit and introduce too many variables into the equation, at least at first.
Given that the dish has been in the same well protected spot for some time, I think it unlikely that it has been moved out of alignment but I acknowledge the very real possibility of having to eat my words later on.
I note that Screwfix - an unlikely source - stock Sky LNBs so I'll call in there on Monday while aged dad is at the hospital. Parking at the hospital is well nigh impossible, so I might as well use the time wisely.
Thanks,
N o t a
PS Yes, I am aware that the dish is of the 'offset feed' variety.
In the early days of satellite TV I was puzzled that dishes always appeared to point at the horizon. Eventually, the penny dropped.