URGENT HELP - PLEASE HELP - F30e has is not working?

MY F30e bolier went off over a week ago and ive been told the problem is low pressue and ive also been told the pilot light has gone out and i need to restart (not re-set) but the plumber from united utilities could see how to restart/manual ignition but NOT re-set . He siad this is the probelm...
the bolier is flasing error code 21 which in manual is low pressue but im on 1bar which iam told is enough - could somebody please help me iam so so so cold and annoyed....
p.s i live in a top flat - 3rd story -possible water pressure is 5liters per hr so i was also told