The Redback surefire is a low middle and more traditional profile than the others! There is the Allegiance model which has a middle more like the higher middle of the Harlequin...
You already know that Harlequin bats are decent as you had yours for 4 years! And they won the AOC 2009 best bat award!
And the Black Cat Shadow is (in my opinion) the best bat you can get for £250 - mine goes like an absolute rocket!
BUT don't forget SAF!!! They won 2010 awards for their bats!
Out of all of these, I would get a SAF.....but that's only cos I already have the other bats!!
But any would be good enough for a player at ANY level of cricket....as they are all quality.
Take your time and look at their profiles, what weights they offer, and look at reviews as people get theirs and see which you prefer.
Best of luck chap.