It depends on how distantly you are involved, do you attend meetings? You could ask the Secretary to put it under AOB at the meeting, telling him briefly what your question is. Alternatively ask the question at the public meeting.
It’s awkward, our local Village Hall was renovated using a mix of Local Authority Funding, charitable Trust funding and Other sources, plus local fund raising in the Village, the building works were done by the brother of one of the PC councillors. When I mentioned it I was told that the Tenders had come in all at very similar amounts but that the councillor had vouched for his brothers work, so they didn’t mind paying a bit more.
To say that I wasn’t popular for asking the question at the meeting would be an understatement, but later another councillor came up and said that I had been brave to ask the question at the meeting as she also had her doubts.
In the end the work was fine, but I still don’t think that it was the way to go.