(I added the labels and red tags, and fixed the box to the wall)
This box is where the wires from fused CP, CH pump, room thermostat, timer and boiler meet.
Obvious flaws seem to be: The use of y/g wire for switched live. The timer says 3A fuse on it, no evidence of one. The terminal block doesn't look quite suitable for a pump rated at 39A
I've never touched CH wiring before, I was just checking it before I replaced the suppressor in the boiler, which I think has been f****n with my FM.