First thing you need to check is your group constitution. If you are a community group run by a management committee you must have a constitution somewhere.
You should also check with the Charity Commission too if you are a registered charity - you could be breaking the rules of your charity if you employ a committee member.
A committee member or officer can help voluntarily within the group, but not to sure about them getting paid!
And, yes, sorry to say, but the Management Committee are your employers!