The recall does include the UK, I've just had two of my house extinguishers replaced as a result.
At least some of the extinguishers being recalled are perhaps unlikely to be on boats as they did not have A/B/C ratings on them, but worth checking, obviously. All the replacements are a single model (so even if you register a recalled car or a kitchen type, you get a standard model KS1KG in return), but the replacements are marked EN3 5A 34B C so could be used towards a boat's complement for BSS.
Details here: https://www.kiddesafetyeuroperecall.com/, took about a week, prepaid DHL bags to send the recalled ones back in.