Glow Worm 30ci losing pressure and F1 Faults?

This boiler has been problematic for a while now. Can only seem to get pressure to 0.5 - 0.6 bar. Then when switch on boiler it pisses water all over the floor. Often fails to light with F1 fault. Reset several times before lighting. Once running seems to be fine. Problem is worst when only using DHW only as pressure drops overnight. Sounds like there's air in system, but raidators have been bled. Any suggestions would be appreciated. This boiler is without doubt the worst I have ever owned.