Paul - title plans for different title numbers are created at different times and based on the Ordnance Survey base map available at the time of that initial registration.
Title plans don't show the exact legal boundary and should be interpreted as such. And you won't have more than one title plan for the same title so there's no 'most up to date plan', just a single title plan for a single title number.
Our PG 40 supplements contain a myriad of guidance re title plans, boundaries and registered extents -
Land registration: Practice guides - GOV.UK