we have a radio service who is able to advise (callsign 'radio').
CJM, the radio operator may be in a position to advise you of other traffic, but you absolutely must not rely on them for this. An air/ground radio service is there to provide you with airfield information. Traffic information is outside of their remit, and you should instead rely on the Mark I eyeball.
Also, at most small airfields, it is likely that the person operating the radio will at the same time be taking landing fees, making the sandwiches in the cafe, answering the telephone, and generally handling any number of other daily flying school/airfield tasks, which means they will often only have a sketchy idea, at best, of what is going on in the circuit.
Regards, jez