Hi Andy,
I also have ME, severely. For both DLA and ESA I wrote on my forms basically what I suggested earlier, and it didn't cause any problems/wasn't challenged.
I had home medicals for both benefits last year, and we (my friend who was present and I) made the same point to the visiting doctors, who didn't seem surprised. Very sorry to hear it wasn't understood at your medical.
I guess it's a bit of a lottery
regards
Rainbowlight