Hi Peter.
The question of DLA - PIP - if you look in the 'Topic ESA, PIP and DLA queries, Gordon has given a full explanation of when and how the transfer fro DLA to PIP is organised.
As for your reassessment for ESA, I am sure you will get your brown envelope nearer the time for the current award to run out.
I doubt that anyone can give you a definite date, or even a good estimate - and I appreciate just how worrying that can be. You WILL be invited to transfer to PIP; you WILL be reassessed for ESA, but exactly when is not definite.