An application to make a payment into court is generally seen as an action of last resort.
Before authorising a payment in, the court may direct further enquiries be made. The costs of the application and any further enquiries are at the discretion of the court and may not necessarily be awarded against the recalcitrant beneficiary, either in full or in part, even if the application is successful.
Are you satisfied that the persons with whom you are in contact are, in fact, the beneficiaries? If you are so satisfied, do you know why they are unwilling, or unable, to provide appropriate ID to comply with your AML procedures?
It may be worthwhile notifying the beneficiaries that consideration is being given to paying the monies into court which, it if goes ahead, will likely reduce the value of their inheritance. Even if this does not result in you receiving the appropriate proof of ID, it might at least encourage them to assist you in understanding why they have not complied with your requests.