Unfortunately, this issue may not be considered a "serious safety defect" for the purposes of a DVSA- backed recall. From the website, things are not classed as a serious safety defect if "you’re warned about them by warning lights, noticeable changes in handling and unusual noises". All the reports here and on the Facebook page note that the system gives plenty of warning of potential failure.
I've been following the posts, both here and on Facebook. This problem is similar to a manufacturing fault that has been identified and corrected for certain Japanese domestic market (JDM) vehicles. It appears that, over time a seal that has not been assembled properly may cause fluid to leak into the electronics housing causing errors to be detected by the vehicles diagnostics system.
The issue for UK owners (and presumably those in other countries) is whether non-JDM vehicles have been assembled using brake simulator modules from the same batches. Due to differences between JDM VIN codes and those for other markets, UK owners only have the date of manufacture as a potential indicator. Only Honda in Japan will be able to correlate vehicles with parts batches.
Dealers should inform Honda UK/Europe of a pattern of failures that can, in turn be reported to Honda Japan. If dealers are only ordering spares, and Honda UK do not spot an unusual pattern of requests (it's still low numbers) a potential issue may not be identified. If all those affected by this problem write to Honda UK, using key words and phrases to trigger automated systems (like those used to process peoples' job applications), they may respond.
As a final comment, it would be prudent for anyone getting a replacement to insist on retaining the faulty item, should, at a later date a systematic issue be identified.