The arrestee should have been able to call their chosen solicitor from inside the police station.
The Back Office may also have called the solicitors to let them know about the arrests and they may have received calls from the police on behalf of arrestees.
Introduce yourself and your role to solicitors and ask to be kept informed. Suggest that they pop out and chat to you once in a while so that fellow activists and legal support know what’s happening. It’s all too easy for them to swan into the station and be in there for hours with police station support outside none the wiser (and in some cases not even sure that they have arrived!)