To be able to deduct the amount from your wages the employer must either rely on a specific clause in your contract or have a prior written agreement through which you consent for that to happen.
If it is a contractual clause then it must be a "relevant provision", which means one that is set out in a written contract which has been given to the worker before the deduction was made. The contractual provision must make it clear that the deduction may be made from the worker's wages.
If they want to rely on a written agreement, the law states that "the worker has previously signified in writing his agreement or consent to the making of the deduction". Similarly, the written consent must make it clear that the deduction may be made from the worker's wages.
So in the circumstances it is unlikely that they will be able to deduct the amount from your ages, unless you specifically consent to it. Instead they can treat this as a civil debt and in the event of non-payment by you they could take it to court. Any repayment must also be reasonable so they cannot just ask you to pay it all in one lump sum if doing so will place you under financial strain.
This is your basic legal position. I have more detailed advice for you in terms of the right you have should they make the deductions from your wages anyway, which I wish to discuss so please take a second to leave a positive rating for the service so far (by selecting 3, 4 or 5 stars) and I can continue with that and answer any further questions you may have. Don’t worry, there I no extra cost and leaving a rating will not close the question and we can continue this discussion. Thank you