I'm trying to work around this but it's proving very difficult.
It's looking like a bug in the GXT codebase to me. The funtion deferStartEditing in the class EditorSupport is always called with a row index relevant to the current page on the grid and doesn't take into account the offset of the page.
This row index is used to get the entry from the store before edit - so whichever page I'm on I'm always getting an entry from the first page.
Would be very grateful if someone could look into this one please.