Sorry about what is happening, but this is how centralized exchanges operate.
I have been trying to withdraw a balance of around 1.2M GBP from Bitstamp for the last month.
£1.2m is such a large anount to store in an centralized exchange, where you don't control the keys and the exchange can confiscate your funds at anytime.
Although their domicile has always been unclear to me (elements apparently in UK, EU, US, and customer relationship apparently being moved between "entities"), it has always seemed to have a UK presence. Therefore, I intend to raise a complaint with the FCA, and with the Serious Fraud Office in London.
From what i found online, their business headquarters is in Luxembourg City.