An annual service is the single best way to keep your boiler safe, efficient and reliable. Most breakdowns give warning signs long before they leave you without heating, and a service is where those signs get spotted.
Manufacturers typically require an annual service by a Gas Safe registered engineer for a boiler guarantee to remain valid, so it is worth checking the terms that apply to your own boiler.
The best time to book is late summer or early autumn, before the heating goes back on and before the busy winter period.