@Bill1968 simplisically it is the wide beam channels that should be lost first. The Ku band microwave signals from a satellite in orbit 36,000 kms above equator are pretty weak by the time they reach your dish. These signals are further disruted by water in the atmosphere but with a 40cm dish in England with a clear view of the sky to the West of South should not lose signal until the weather is appalling, heavy snow being the worst. If your dish is partially blocked by trees you will inevitably lose signal more frequently especially as trees grow..
In practice the tramsmission power is limited by the power the satellites solar panels can produce but the aerials can direct the signals into a beam the wider the area that covers the lower the signal level is on the ground but each transponder can be tuned to optimise coverage but simplistically you would expect the UK spot beam channels to be more reliable.
Also various technical tweaks can improve the threshold before signal errors cause the loss of service. As a guide the free to air channels like the BBC and ITV are on the spot beam transponders to make reception beyond the UK more difficult. Encrypted channels are often on the wide beam transponders.
If people are interested this page gives details of the Astra 2F satellite including the various beam maps see http://www.astra2sat.com/astra-2f-satellite/. Ignore the Ka band as that is not for TV use and the West African beam is clearly not used for UK channels. The move by the UK free to air channels to the UK spot beam explains the huge dishes you used to see in Southern Spain and the Canaries but now streaming has largely made these redundant.
The useful Lyngsat site shows the beam each transponder uses in the left most column https://www.lyngsat.com/packages/Sky-UK.html
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