I'm playing as Kiddy Harriers and I;ve just signed Paul Jones (ex Harriers LEGEND) and even though he's 42 and 111 days by the time the season starts, he is awesome. My coaches advised against him but he's played 4 games and has a rating of 7.20.
And he gives a massive boost to your defence confidence.
With re: to a CB, i signed Sagi Burton, who is a St Kitts & Nevis international and he too is excellent for a free. YTou have to be quick though as he gets snapped up pretty quick by a league 2 club if your not sharpish.
Also there's a guy, Beckworth, available on a free.