The 'big boys', NatEx and Stagecoach have, in many cases, seen off competiton from local operators from towns and cities where they offer cheap advance purchase fares.
One local London scheduled coach service dear to my heart is Berry's Superfast from Taunton and other Somerset locations (and Tiverton across the border). This continues to be very popular, I guess because of the lack of competition from either National Express, who do not offer their advance Fun Fares from Taunton, and from Megabus, who do not operate in the area.
edit - I have split this off from the topic about Baker's Dolphin as it deserves its own thread - G
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