Yes, they’re required to be serviced on a yearly basis by a competent person to BS5306:3
To comply to the British Standards BS5036-8:2012 Clause 8.2.1. there should a minimum of two Class A extinguishers required per storey up to 400m square with a combined fire rating of 26A.
The British Standards aren’t a legal document but a guideline to work to but would be used in a court of law if required.
The only fire extinguisher designed for deep fat fryers is a Wet Chemical extinguisher, which also tends to be an insurance requirement.

Some companies install a Powder extinguisher but these aren’t suitable as they don’t tend to extinguish the fire and can create more of a hazard by possibly inhibiting escape or rescue attempts caused by the powder cloud. A full deep clean would be required as well as loss of food stock due to contamination, which could cost thousands in expenses and lost revenue.

YES, under The Regulatory Reform (Fire Safety) Order 2005 it is a legal requirement to have a recorded Fire Risk Assessment and must be reviewed on an annual basis.