It is pretty much the same in the US. The reason they can offer people a low cost classic car insurance rate is that there is an understanding that the person has another policy for the daily use cars and they usually want proof of other insurance. If you follow the rules, they usually won't deny a claim unless you exceed their mileage maximums, if they have that, or you violate usage rules (you can't use your classic as an Uber driver, you can't use it in a Business capacity). If you have a claim and when the adjuster sees that you had 48 two-by-fours/lumber strapped to the roof and you had an accident leaving Home Depot, they are not going to not like that. If the policy stipulated that the car be stored in a locked garage and you don't even have a garage and hail pounded your car in the driveway, they are going to not like that, either. If it excludes track days and you wreck at the track, no coverage will apply.
Mostly if you reasonably folllow their rules, they'll treat you right.