This layout is evolving as it slowly progresses and one bugbear was the bottom corner. I didn't want to see trains on the sharp curve! However, I started off by shaping some rough timber with a jigsaw as a basis for an embankment....
I discovered that if I used the slightly sharper Set Track curves, there was room to insert an almost straight section under the bridge. Signs of the original curve are visible on the baseboard .....
The shot below gives a better idea of the modifications. I'm currently awaiting Code 100 track and turnouts for the fiddle yard. The Hornby Riddles 2-6-0 negotiates the Set track curve without fouling the front steps. All the Code 100 will be pinned down to give much quieter running...
Track level view to see how things will look ...