My car was involved in an accident that was no fault of my own, and my car was written off however when my insurance paid me out they deducted £200 (pound) of the amount that was agreed, a they said I would have to pay the access and would be paid it back once the third party had paid out to my insurance, now the claim has been settled by the third party and my insurance has paid out, my insurance is refusing to pay me back my £200 (pound), what can I do to try retrive the money back...

I don't understand what "pay the access" means. It's a new term to me. If you had collision coverage with a deductible, they should have paid the value of the car less the deductible. If they recovered anything from the other driver, then they should have reimbursed your deductible. At least that's how it works in the US (I assume you are in the UK).

Deductible = Excess (access in this case)

Yes, that's how it should work..

If they settle with the other company for less than the full amount, then they did not get paid the excess. So in talking to the insurance company did they give you the information on the total settlement they did with the other company.

If your cost was 2000 and they settled for 1500, they never got back your 200 they held out.