Ah, here we are - the relevant bit of the practice guide:
3.2 Registration of a disposition by the personal representatives
The personal representatives of a deceased sole proprietor of the registered estate, or of a charge or mortgage, may, without first being registered themselves in that capacity, deal with that registered estate or charge. They may do this by way of a transfer, or a transfer by way of an assent or appropriation using the appropriate form in either case. To make an application to us you will need to send us the following.
Form AP1 (form FR1 if the transfer or assent triggers first registration).
Either transfer form TR1, or TP1 (if you are only selling part of the registered estate), or assent form AS1, or AS3 (if only part of the registered estate is the subject of the assent).
Either transfer form TR4 (if the deceased was proprietor of a charge or mortgage) or assent form AS2.
The original probate or letters of administration, or a court order appointing the transferor as the deceased?s personal representative, or (where a conveyancer is acting for the applicant) a certificate given by a conveyancer that they hold the original or a certified copy of the probate, letters of administration or court order. We will not need this evidence if the personal representatives are already registered as proprietors in that capacity.
The fee payable under the current Land Registration Fee Order.
NB1: Any transfer by the personal representative(s) to the beneficiaries should be accompanied by a stamp duty land tax self-certificate.