Failure to attend Tribunal, setting aside a decision ...

Hello !
Have a cl who failed to attend tribunal 13/02/12 because he was not well and lost his ESA appeal.
Cl has also been experiencing personal problems relating to one of his children.
I am considering asking the Tribunal Service to set aside the decision, I know this request is outside the one month time limit, because cl. could not attend but in the meantime what does cl. do ?
The initial decision that cl does not have a limited capability for work was 12/09/11 so cl can reclaim ESA on the same basis from 13/03/12, but this means cl loses a months money.
However, if cl. GP was willing to provide backdated medical certificate to 13/02/12 which clearly states his health got significantly worse since 12/09/11could cl. reclaim ESA from that date and have it backdated.
However, because we are having to ask the Tribunal Service to set aside the decision, what does cl have to do while we wait for a decision on this request.
Hope I’ve made sense, been a very manic Monday, but any ideas greatly accepted.
I think cl has to claim ESA on either of the above grounds but ...
Thank you