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Welcome to the forum, you might want to have a look at the following FAQ which explain where everything is
Welcome to Benefits and Work Are you sure that you can score the extra points that you need for an Enhanced award?
If you are then contact the DWP in writing and ask to be reassessed on the basis of a deteriorated condition. Be aware that this will result in a new claim form and almost certainly a face to face assessment.
Providing you have a PIP award prior to your 65th birthday then you can continue to receive PIP after you are 65 as long as you continue to meet the criteria for an award.
Gordon