Geoff, I have seen some Hymers with a RHD Drivers door, however our first A Class, was not one of them.
Incidentally we never use any cab door, keeping the floor nice and clean. We only use the hab even on our now normal cab!
I said some A Class do not have cab doors. The ones I have seen have usually been RHD passenger/nearside doors, i.e. standard spec for a continental version of that model. I think a RHD driver's cab door would have been an optional extra.
Any cab door on an A Class does reduce the available extra shelf/stowage space which is one advantage of the bigger cab.