VICTORY!!!!!
After taken advice from you guys and talking to a solicitors I withdrew my claim from the letting agents with much regret....I contacted trading standards and made a formal complaint against the letting agents..but was basically told there wasn't much they could do except log my complaint..anyway I wasn't going to give up so I sent them the following letter...
Dear Mr Harrington,
I am writingg to advise you that I have withdrawn my claim against your firm after seeking legal advice with much regret.
I have been in contact with my landlady she has assured me she has not got any monies from my deposit.You have invoiced and charged me 275 pounds for clearing and cleaning the property.I have gained access into 14 ****road and have photographic proof this work was never done.(please find enclosed photos).
You have also charged me for an extra weeks rent.
Please find enclosed copy of print out from your firm which clearly states that I have been paying my rent on the 5th of every month since june 2005.
Please note that I had advised a member of your staff on the 04/08/06 that I would be moving out by the 9th sept(Hannah)
The actual date I moved out was the 8th sept.I came into your office on the 29th sept and paid 59.16 for the extra time I had stayed in the property.
My calculations Deposit 900
deductions 2 arrears letters -25.26
deductions bounce4 cheque -29.38
= 845.36
Due to no work was carried out for the clearing and cleaning and to your staffs incompetance in keeping records you owe me 845.36, which you should pay to me immediately.
I have made a formal complaint to Mr.***** at Trading standards in Brighton and Hove city council with regards to invoices which you have given me for work which was carried out and also photos showing this was not done(they have copies of this), I believe this is a breach of the Trade Description act 1968 you can discuss this matter with him if you wish on ****
I do not know why you have withheld so much of my deposit except for personal gain.
I can assure you that I will pursue this till I get my money back,my next steps would be to contact the local press and get my friends and family to protest outside your firm.
In the interest of the reputation of your company you wouldn't want me to do that would you?
I look forward to your response.
I sent this by recorded delivery
LORD AND BEHOLD!!

..a cheque for 707.86 arrived the next day and the following letter..
Dear miss blah blah blah..........we do not take kindly to threats in relation to our office.If any protest is made outside our office we will have no choice but to request the local authority/police to arrest you for a nuisance.
However to try and compromise this matter we now enclose a cheque in full and final settlement of your deposit in the sum of 707.86 being the 275 which we have clearly deducted and have taken place but we have divided this by 50% and now enclose the balance of the cheque.If you return this then we will have no choice but to continue to fight this matter through the courts which we will have no hesitation in doing so.
ha ha!!
Iv accepted the cheque only because my landlady has already given me 200 pounds...so Iv managed to get all my deposit back...Iv had to wait 6 months to get my deposit back...loads of stress bangin my head against brick walls...only to find good old fashion protest is the only thing that works....

good luck to everyone who's going through what I had to go through!!