How to make a start

After realising the potential task with the time I have available, I have been putting some serious thought into what do to get me started. A small diorama/working layout may be the best starting point. I am trying to think of ways that if this is successful whether it could be constructed in such a way that it could become part of the Grogley Junction project. Or at least a stepping stone onto Grogley.
So first thoughts being:
1) How would Boscarne Junction look in my alternative universe?
2) How would Ruthern Bridge look?
3) Could I get enough out of building an extension to either of the three lines leaving Grogley Junction?

Boscarne, as it may have been if Grogley Junction was build as I propose, could be a good starting layout. Should be able to get this junction down to three points. At a later date may be able to justify a small wharf siding, feeding the Mill perphaps?

I am beginning to like the idea of Ruthern Bridge but as I commit pencil to paper the track plan always ends up to be more than just a test layout. This would have a good range of traffic with thought traffic between Grogely and Mawgan Porth also Grogley and St. Blazey. Plus if I really stretched the plusable history to it limits, the addition of a branch to the mines near Withielgoose Mills and on Mulberry Downs. Not sure what these mines were, (Iron Ore, Tine, Lead or Copper) but the extra interest in traffic and track layout would add to the operation.

To build an extension to any of the three exits to Grogley could be a quick way of getting started. An extension to the line off to Mawgan Porth would be especially good as it could form an excellent bridge between Grogley and Ruthern Bridge. Though how would I gauge the end sections? How much value would I gain as there would be no real track building, no points to construct. It may be better to build these once both layouts are build so that end pieces will match.

So Boscarne it is?!!! Well for the moment anyway.