When a bank submits a SAR to the NCA the account gets frozen for 7 days. In this time the NCA can respond to the bank to say no further action or keep the freeze on, they can extend it for a further 31 days. After this period if they wish to extend further they must apply to a court.
I would note that the FCA guidelines and case law state that to submit a SAR to the NCA it should have reasonable grounds which are not fanciful . An unusual customer or a transaction that is fishy is not sufficient.