During the Edinburgh race, Dot and her new mate keep up with the main pack right up until their bike breaks down. But their bike's an Ariel Arrow - 250 cc, ridden 2-up - so it's unthinkable that it could keep up with much-more-powerful bikes with single riders.
It's not clear exactly what time of year the film takes place, but it's certainly cold - yet the characters undertake long high-speed motorbike journeys with no fairings and indifferent clothing. They would be frozen to the marrow like non-bikers can't imagine - but show no sign of it.
When Dot goes to her Mother for Sunday lunch, her Mother gets food out of the oven without using an oven glove. This would have scalded her if the oven was on, heating the food.