Central heat electrical system? I need to replace my outmoded central heat programer but while reading...

I need to replace my outmoded central heat programer but while reading through the info that came near the boiler i found a piece of paper for the boiler that said to operate self diagnostics it wants a permenat live supply live, nutral & earth from a switched fused spur.
The programer electrical system diagram shows that the boiler should be conected to the wiring control center / fork box and is not conected directly to the live but via the programer and thermostats.

Which way is correct or best?

The boiler have a 5 terminal connector with a small pullover cable across the back if i remove this can i next wire the boiler directly to the D (via the wiring control center/ fork box)and have a seperate switched live from the electrics center controled by the programer and stats, using a 5 core cable?

The boiler is a Ideal Icos, the controls are all Honeywell and i'm using a 3 port mid position spigot (Y plan setup)
Shrinkage contained by table top timber,who's bad habit...
Answers:    That is beyond DIY in my book anyway and I would suggest you phone the pro's in, sorry.