Out of interest could you give us some examples? I've had a look and other than the U23s Premier league I'm not finding anything useful.. I think Coventry do, but then i'd not put them as a similar size club.
Cheers
There is an Under 23 Professional Development League, this contains teams such as Crewe Alexandra, Wigan and Barnsley in the North Group, with others such as Ipswich, Charlton and Colchester in the South Group.
U23 Premier League
U23 Premier League 2
U23 Professional Development League