Ferroli Optimax - no hot water ?

Hi, I hope someone can help me.
I have had no hot water or heating for over 5 weeks. I have boiler cover through my energy provider and they have basically replaced what seems like all of the parts of my boiler and still it does not work.
Originally it started with a F01 and the whole system would not work. Parts were replaced including some kind of valve, and a probe (forgive me, I can't remember the names of the parts and no paperwork was ever left)Still wouldn't work. More parts ordered...still disn't work. So, the gas pcb has been fitted, something to do with the condensate as something was stuck, a new hot water board. The fitting of this caused the new pcb to blow which has now just been replaced again. The heating actually works now, but when the hot taps are put on, the pressure gauge rises very fast. The man has left the boiler on so as I have something working, but I am sick and tired of boiling kettles and pans for washes for a family of 4 for 5 weeks.
I have been warned that my insurers will probably not pay for anymore parts under my policy. Do people think that it probably should have been a simple job???
Problems started in the cold snap when my pipes were frozen. After that I had to repressurize the system every morning because there wasn't enough pressure. And then there was a problem with too much pressure and the pipe outside was always running.
Sorry for the super long post...as you can probably tell I have had it up to here!!!