Hello Marion
First, change the boiler man. When you have found another, ask him to pressurise the expansion vessel, when it is empty, up to 10 psi. When that is done, the whole system should be filled to about 1 bar and the boiler switched on. Expect the pressure to rise to about 1.3 bar after a while. The pressure should remain constant. If it doesn't, there is a leak somewhere, so check the overflow outside before panicking.
John
October 2009