You can get the NOTAMs for the UK from the FAA at
https://www.notams.faa.gov/
The ICAO identifier for the LONDON FIR is EGTT.
They are also available from the Dutch the link in my previosu post. (NOTAMs = Double Dutch
)
Apparently the AB 5123 part of the NOTAM is the reference within the AIS Bulletin. The H3365/02 part of the NOTAM reference is it's real-world reference. The documentation on the NOTAM system available from the FAA site in my previous post are applicable to NOTAMs in their RAW form. (The FAA NOTAM site offers the choice of Report Form or RAW form; the Dutch site only offers the Report format - easier to read, but documention makes less sense)
Mystery solved?