Yes, not having ordinary fire extinguishers serviced can be a criminal offence.
Maybe worth mentioning at this point is that, after five years of development, Britannia Fire has now introduced the Fireworld extinguishers, a UK manufactured fire extinguisher that is guaranteed for ten years and does neither require servicing by external engineers nor refilling after five years. These Fireworld extinguishers still must be visually inspected by the owners or their representatives, however no special skills are required.
Unless your business has Fireworld extinguishers installed, a yearly fire extinguisher service must be carried out by competent persons, which usually means a fire service engineer.