The number of people who are in receipt of Personal Independence Payment (PIP) and who previously received Disability Living Allowance (DLA) can be found in Stat-Xplore under the PIP claims in payment table: https://stat-xplore.dwp.gov.uk/. These statistics provide a breakdown by parliamentary constituency and reassessment indicator of the number of PIP claims in payment each month since PIP was introduced in April 2013.
It should be noted that the PIP claims in payment table gives the number of people in receipt of PIP at the end of the chosen month.
Guidance on how to use Stat-Xplore can be found here:
The number of disallowances for PIP for claimants who previously had a DLA award can also be found under the PIP clearances table in Stat Xplore and can be broken down by parliamentary constituency. This data shows the initial DWP decision only. Replacement benefits could include PIP and Attendance Allowance (AA) for those who are eligible.