Oh dear stonekicker, wait till you get all the facts before giving advice. Most ASTs wont have a clause allowing the tenant to break the tenancy in the first 6 months - there would be no point having a 6 month fixed term if that were the case. The 'arbitrators' of the tenancy deposit scheme wont be interested either as they will know nothing about the deposit. The arbitrators will arbitrate on any deductions from a deposit held in the scheme if both parties agree to the arbitration.
Whether the deposit had to be held in a protection scheme or by an insurance policy depends on the date you signed the tenancy or resigned a new tenancy and the type of tenancy it is. If it was after April 2007 then, in most cases, the deposit should be held in a scheme and you should have been informed of this. If the deposit should have been in the scheme its possible for you to sue the landlord for 3x the deposit. A few cases of this have gone to Court and, from what I believe, judgments have gone either way. Unfortunately, the Law in this case isnt written particularly well and it's fairly ambiguous.
If you broke your tenancy agreement by leaving early or without giving the required notice then the landlord can use your deposit in lieu of the rent you owe.
If you feel you are owed money back from the deposit then you would need to first of all write to the landlord stating your reasons. If youre not satisfied by that then you could take the landlord to Court, you can do this online quite easily.
I'd listen more to Jenna1978 on this than stonekicker.