Hi Sam. As you probably know NOTAM are messages and as such are ephemeral in nature. For years now the UK has populated the European AIS Database (EAD) with UK NOTAM. EAD is run by Eurocontrol and also receives worldwide NOTAM from the NOTAM offices (NOF) of ICAO member states which also feed into the database. This enables them to provide briefing tools to select NOTAM for inclusion in PIB (preflight information bulletins). As far as I know the public facing functionality does not include a facility for expired NOTAM to be searched. I do know that UKAIS did (and presumably do still) have access to PIB served through EAD for 30 days so that in the event of an incident the PIB can be pulled to see what information was requested by and served to the logged on user. It's normal for any database to be periodically parsed of obsolete records in order to keep its size down and keep search times short. How long the NOTAM data is kept in the EAD I don't know but your best bet would be to call the UKAIS Supervisor on 01489 612488 or 01489 612489 who should be able to assist you.