Wow! Thanks for all the comments - very motivating

I've now completed the building of all the tiles so the next stage is to paint them, beginning with an undercoat of acrylic Burnt Umber (without added water) from The Works (discount store).
The whole board so far:

The Inn entrance: fine beach sand used for the road and for brushing into gaps, coarser sharp sand for the grassed areas.

The side of the building showing where sand and dilute glue were used to create an uneven ground level; in the background is the ford.

The bridge with brushed-in sand.

The track up the cliffs with levels that minis can stand on.

Stepping stones (infantry only).

The waterfall and river.

The cliffs (with a lot of the cork boulders now covered by sand).

After painting, I'll add the water effects.