You are indeed correct. The legal title has passed to A, and so that a sufficient receipt for Sale monies can be given to the Buyer, A merely needs to appoint a second Trustee in the Land Registry Transfer, and this second Trustee will just need to sign the Transfer together with A. A's Solicitor could be this second Trustee.
I hope this helps.
Thank you. So for the avoidance of doubt the grant of probate for A would not be required?
Correct- Probate is not required for the Sale whatsoever.