Most car warranties will stipulate minimum care criteria for your vehicle. Any car warranty you take out will only be valid if you have an up-to-date MOT and have had a service in the last 12 months.
Some providers, usually franchised dealers, will require you to have your MOT and service completed at a listed garage, rather than your choice of independent garage, for the duration of the car warranty. This is often a good way for the provider to guarantee repeat business but can mean that you pay more for these services than you would ordinarily.
Check if this is the case and whether you’re happy with the servicing arrangements before you buy. Some providers may even help you by providing low-cost service and MOT arrangements.