I've found this committee session from 2023;
14 March 2023 - Post-Brexit UK-EU security cooperation – follow up - Oral evidence
https://committees.parliament.uk/event/17670/formal-meeting-oral-evidence-session/
I think if you read the oral evidence from Peter Ayling, International Crime Coordination Centre Lead at National Police Chiefs Council and Steve Rodhouse, Director General Operations at National Crime Agency, it will offer some reassurance, e.g.
We have made some good progress, I think, in minimising the issue of live time access. When the UK receives Interpol notices from member states, they now go through a process and almost all are available through the Police National Computer to officers on the front line within a small number of hours. [officers could then access this information within minutes]
There is no doubt that we would prefer to have kept SIS II, but the mitigation in place through the use of Interpol notices and relying on the I24/7 database has been shown to work. I think you can see that with the number of notices that are put on to the system and the work that has been sustained.
As of this month, the UK is now connected to 15 countries across the Prüm network for the sharing of DNA— that is 95% of all DNA profiles held in Europe—and 12 countries for fingerprint searching but with a further five countries to come on stream. That is a significant capability
I do not want to give an answer specifically around counterterrorism arrests, but I can certainly assure you that our officers are able to make arrests in the UK through the National Extradition Unit, and are doing so effectively. Equally the UK’s ability to access support and co-operation abroad from people is there.
They also discuss a new programme I-LEAP - described here;
Phase 1: will deliver connectivity to the fixed INTERPOL’s network database (FIND) system, providing real-time access to INTERPOL nominal data to UK policing, whilst expanding access to other INTERPOL datasets. These services are being rolled out nationally to policing, the UK Border Force, and the National Crime Agency (NCA).
https://www.gov.uk/government/publications/home-office-major-programmes-accounting-officer-assessments/international-law-enforcement-alerts-platform-i-leap-programme
Starmer tried very much to get access to again in the EU with good reason, but they refused. It would've helped massively with the backlog of cases that they inherited.
At the end of 2024, the UK had the 5th largest backlog of cases - why didn't those other countries (France, Germany, Spain, Italy) deal with their backlogs much quicker?