Mark,
I thought it might be helpful to start a separate thread on this. I hope you don't mind.
I've just done some measuring up and the big Beachtown layout fits in a 7'6'' x 4'8'' space, allowing for a bit of room outside the area..
I'll provide measurements for the other modules (i.e. Seaport, the quarry siding, Farm Halt and Pond End). These can be joined directly to each other or have track between and can be swapped in and out as space allows, although Beachtown and Seaport are designed as termini and so are essential to a layout.
I'll post plans of the modules with their sizes.
As yet, the bridges aren't in a module but that will probably change.
However, nothing is written in stone.