How can I fix pressure & ingition problem - Vaillant TURBOmax VUW 242E/282?

I have a combination boiler (Vaillant TURBOmax VUW 242E/282 E).
A couple of days back I had problems due to reduced pressure and air trapped in the system - [pressure gauge indicated the pressure as (approx) zero]
I had following problems -
1. The boiler was making a noise
2. one radiator was warm at the bottom but cold at the top
3. The boiler failed to light… and the burner lockout indicator was illuminating.(It started working again when it was reset)

Yesterday I noticed a little bit of water & soot in the boiler cupboard and in the evening the boiler failed to light and the hot water supply stopped.

What should be done?