OK so Phil gave the idea of an obese man who has died in his caravan and needs to be collected. I'm not too sure if it's the job of an undertaker to collect dead bodies from the scene of death. I've looked for the answer on the net and it seems it can be but it just depands on the circumstances.
But going but that premise here is a rough outline of a story.
Undertaker goes to caravan in the middle of nowhere (woods) to assess the logistics of transporting Mr 'My God You're A Fat Bastard' out of his caravan that he has grown into. After many comedic attemts to extract Mr MGYAFB (Blow torch, angle grinder, blah de blah) and failing it is decided to bury him still in the caravan effectively using the caravan as a coffin.