Help needed with ESA... support letter from GP

Hello all, I'm new to the site...so bear with me if I'm doing this wrong
My husband was moved from Support Group ESA to WRAG last year, DWP triggered a Mandatory Reconsideration when my local MSP (we live in Scotland) phoned them to complain about the decision...we weren't even notified, we just received a Mandatory Reconsideration Notice upholding the original decision.
This meant that he will stop being paid ESA unless we make a new claim for Universal Credit...which we really don't want to do. We spoke to CAB who suggested that we apply for an 'anytime review', to say that his mental health has deteriorated in the last few months ,(which it has... because of this), but said we need a supporting letter from our GP.
I asked our GP, explaining what is happening, and she is more than happy to help...however, she doesn't know what information the DWP needs, and what would be the best thing to write on his behalf (he has a long history of mental illness, as well as idiopathic epilepsy,but no seizures in the past couple of years.
What I really need help with is if anyone knows of any guides or template letters I could give to my GP, so that she could help us to get my husband moved back into the support group.
So sorry for such a long, rambling post!
Thanks

Thanks Gordon....Yes, he is at the end of his contribution rate ESA. We had someone from CAB come to advise us, and she told us that we couldn't claim IR ESA, as this was a full service UC area, and the only thing we can do is claim UC, which we don't want to do,if at all possible, for obvious reasons.
I have been in touch with several DWP departments, as they're currently dealing with complaints I made over a year ago (after the Minister for Disabled, Sarah Newton read an email I sent and made them look into it!)
I have since sent 5 emails back to CAB, but no one is getting back to me, so we're totally lost.
I'll read the links you sent me tho,thanks!
Beccy

Thanks Graham! To be honest, she was fairly useless! It's a real shame, because i've had their help before, when I was still down in England, and they were brilliant! I know that in the main, they're really good...but this one wasn't. She didn't do, or show us a breakdown of what we can claim for...she just told us the only choice we had was to claim Universal Credit, as IR ESA "doesn't exist" now...it has to be a new claim for UC!
I have tried to clarify this, and get the detailed breakdown, but 5 emails later, I'm still waiting.
I have also got to renew my son's DLA claim at the same time, as well as waiting for a Complaints Resolution Manager at DWP to send his response to 3 letters of formal complaint from myself and my local MSP, that have been ignored since last July!
As you can imagine, it's all a bit full on here!
Thank you so much for your help... Beccy