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It is not a given that because you have reached State Retirement Age that any new award will be an On-Going one, it is down to the Decision Maker to decide whether there is still a chance of changes to your limitations.
As to your Mobility. Your current award can be increased providing the DM accepts that you met the criteria for an Enhanced award in May 2023.
Reporting a Change now will not result in an increased award as the PIP legislation prohibits increased PIP Mobility awards once the claimant has reached SRA.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems