Although I would put the Grand Prix only marginally above religious clap trap in my interest stakes, it is a stupid decision to switch the race to another channel halfway through. Especially, as you have highlighted, people may record this to watch at a more sociable time of day.
They should use one of those 'press the red button' type channels for minority interest sports, such as religion, but imagine the furore that Beardy would kick up if it was taken off BBC1.