Hi Graham - the very simple answer would be No as you don't transfer in the way you are suggesting.
When a joint owner dies the legal ownership passes to the surviving joint owner to deal with, for example transfer. So you are the only Transferor in your scenario.
The TIC aspect you refer to relates to your beneficial ownerships/shares. That needs to be considered with regards who is actually going to be registered as joint legal owners and that will most likely depend on how the trust is set up.
You refer to the 'trustees of Property Trust' and your being 'a trustee' so you may wish to seek legal/wider advice as to how the trust is already perhaps protected or options to consider re doing so/transferring the legal ownership when you are actually fulfilling the roles as legal owner and trustee already.
Our PG 24 offers a degree of registration guidance but it's really legal/wider advice you need here re options for both you and other trustees/beneficiaries as appropriate
Practice guide 24: private trusts of land - GOV.UK
However you may have already done so and if you are wishing to transfer the legal ownership/title then you are the sole Transferor and only need to execute the form TR1 the once