Dealing with death of co-owners and their beneficiaries

I need assistance with dealing with a matter where a property is held by four people as tenants in common. 3 out of the 4 co-owners have died but the title has not been updated to reflect this. The property is not in the process of being sold but the beneficiaries of the deceased co-owners want the title to be updated so that the title is in their names. I understand that an Assent can be lodged for the deceased co-owners' share in the property but there are many beneficiaries. As only 4 names can be on the legal title how can the Land Registry place all of the beneficiaries' names be on the title? Or is it the case that one beneficiary per co-owner is nominated to be the legal owner and a trust deed is entered into between all of the beneficiaries with the inclusion of a form A restriction?

Dawn - firstly you can't assent a share of the legal ownership as it is always transferred as a whole. In your scenario, and if the beneficiaries wish to be added as legal owners, then the surviving owner would need to transfer the whole of the title/legal ownership as appropriate. Ultimately some see that as a transfer of a share as that's what's achieved in one respect but that's not how it works in legal/registration terms
I say 'if' the beneficiaries wish to be added as legal owners as they all need to consider what that means and how that might impact on them legally/financially and more. For example a beneficiary might not own another property but by being added as a legal owner here then when they buy their first home it could impact re Stamp Duty. It's important therefore that everyone considers the specific circumstances and what options exist and which is 'best' for each of them.
We register the outcome of such decisions so can't advise you on what the options are or what's best. 
If the decision is for the sole surviving owner to transfer the property to 5 or more names then that's fine but on applying to register the applicant needs to make it clear as to which 4 names are to appear on the register. The number is limited to 4. 
If they enter into a trust deed or wills that split their beneficial shares etc then they can complete the Transfer to refer to that arrangement and apply for a form A restriction. That's all explained in how to complete the form TR1 (Transfer) - Registering land or property with HM Land Registry: Change the registered owner name - GOV.UK