Thanks for all the ideas, gives me lots to think about! I'm basing the layout in the late 50's/early 60's, to be honest I hadn't even considered a region.
The run-around loop is designed for two Mk1's so you're right that moving the points around wouldn't make much difference, a three way point could be interesting (are they much more complicated to wire up than a standard point?). My thinking is the bay platform would be used for multiple units.
I like the idea of rotating the station a bit, I wasn't overly happy with how everything was parallel (hence the weird curved siding!), hopefully I will have a bit of time tonight to play around with the layout.
Using cassettes is a good idea, I guess I would still need an extra baseboard to support the cassettes and then have a scenic section at the front. I'm thinking maybe I can move the entrance to the cassette towards the edge of the board so its not wasting space.