How to manage a client move

My client has moved on to another accountant. They have sent an e-mail to me and the new accountant confirming this, but as yet, I have heard nothing from the new practice (no clearnace, info requests, etc).  This e-mail was sent nearly 2 months ago now and I would like your views on the following:-

1.  I have all my client files ready to return and propose to send them back to the client rather than the new accountant in the absence of any communication from them.  Do you agree?

2.  What information should I keep regarding this client and for how long, i.e. copies of workings, etc

3.  Whose responsibility is it to inform HMRC about change of agent? This client still has me logged as their agent on the system.

Thanks in advance for your advice