BS 9251 Clause 5.9.1 does state that sprinkler heads should conform to BS EN 12259-
14, but gives a bit of leeway i.e., or ‘another residential head standard’, if the approval standard is acceptable to the AHJ! You can check on sites like Redbook Live (and/or other approval sites) for a list of sprinkler heads that have third party approval to BS EN 12259-14