Philip
I would confirm that the DWP have accepted your request for an MR, they do regularly "lose" requests made over the phone.
Assuming the request is being processed and you are happy that you covered all of the issues you had on the phone call then you do not need to provide any more information, however, if this is not the case then you can send them a letter with the additional information. If you do this then make the DWP aware of this when you contact them or they may make a Decision before they have received your letter.
If the MR does not revise the Decision in your favour then you can go onto appeal.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
