I don't think i would have an issue will a narrow boat - apart from anything else, they're quite narrow! (except the huge barge thing...). They were just pleasure cruiser things which took up altogether too much room, two of them were on the wrong side of the river, and they towered over us rather alot...
Are you actually moored permantently in cambridge, or just for weekends/short times? I thought you were outside of cambridge, but then you mention Jesus lock...