Here's my attempt at modifying a Dapol, square post, GWR signal.
1. MSE lenses.
2. Backlight. Drilled a hole in the lamp.
3. Modified the blind, so the backlight is visible when the signal is on.
4. Repainted the post.
5. Fitted a dummy operating rod and balance lever.
6. Works off 5v DC. The lamps look more realistic.