Workbook is of type TsWorkbookSource which is what I'd expect, but what is Worksheet if its not the WorkbookGrid? Where is it on the form and how does it relate to the Grid?
No. A workbook is a collection of worksheets, and a worksheet is a collection of cells - these are nonvisual data structures. The WorksheetGrid is something like a StringGrid and displays data stored in a worksheet. In the same sense that a TListbox displays data stored in a stringlist.
The entire fpspreadsheet library consists of two parts: the nonvisual data containers with TsWorkbook (type of workbook), TsWorksheet (type of worksheet), TCell (type of cell) etc., and the visual controls such as the grid or the mergeaction. The workbooksource is a link between these two parts. It watches for changes in one part and transfers it to the other part. Example: you type something into the grid then the workbooksource passes the new cell content to the underlying worksheet. Or conversely, you change a cell in the worksheet by code, e.g. worksheet.WriteText(0, 0, 'abc') then the grid is notified to repaint itself to display the new cell content.
I've been through the tutorial again, but can't seem to get things straight in my head, any guidance would be appreciate to get me going on the right track.
In addition to the tutorial, also look at
http://wiki.lazarus.freepascal.org/FPSpreadsheet which focuses on the "data-container side" with worksheet and workbook
BTW I can't find any help files in the Lazarus install directory, where should I be looking, and when I press the context sensitive help (F1) it says that it can't find any help - does this sound like something has not installed properly?
No, there is no context-sensitive help, i.e. F1 does not work. But there are chm files in the folder "docs" of the fpspreadsheet installation which you must open by double-clicking. As I wrote earlier these are copies of the "historic" online version and fit to the version you installed; this is because the online version is continuously changing and may describe features which are not yet in your installed version (but only very rarely - and version 1.8.4 is almost the same as the development version).
it appears that Gird column A is 1 where as Workbook.Worksheet column A is 0 - and same for rows.
Yes, this is certainly a major annoyance to a new user: worksheet indexes start at 0, i.e. cell "A1" is row=0, col=0, and worksheet methods expect the indexes in exactly this order - row first, column last. In the grid, indexes start at 0 too, but the 0th column/row are usually occupied by the fixed cols/rows, and the first data cell is at column=1 and row=1! And to confuse you even more, the grid expects indexes in the order column first, row last, i.e. the exact opposite of the worksheet. This is due to historic reasons and cannot be changed any more without breaking user code. So, please be careful.