Hi davem
You are correct when you state that after you reach pensionable age if you are on standard or low rate mobility you are not eligible to claim the enhanced or high rate mobility when you are re-assessed.
The relevant age is 65 or State Retirement Age, whichever is the higher.
You cannot be awarded the Mobility as a new or an increased award after you reach the relevant age with the exception of the initial transfer from DLA to PIP where the age restriction is suspended.
If you have a Mobility award before the relevant age then you can continue to receive it after as long as you continue to meet the criteria.
MRs and Appeals remake the Decision being challenged and apply from the same date so if the MR or appeal takes you past the relevant date you can still receive the Mobility Component if awarded as long as the original date was before.
Gary
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
