Hi mixman09
I can't say very much on this one. You know how these people support you. Have a conversation with them and make sure you agree on what they do for you. If there is anything you don't want them to say, you need to tell them. If they are not used to dealing with the DWP, make sure they are aware that the DWP may raise a question they don't understand or think is irrelevant. Tell them not to answer a question if they are unsure. If they are likely to contact your GP there is very little you can do unless you go and see them and say they are likely to be contacted. Most GPs won't write any sort of letter (though some do for a cost). Normally, they only contact one person on the list, and it could be any of the people you listed.
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems