If the radiators are hot the rads are hot. The boiler's job is done.
The pressure of gas with the boiler off and when it is running is largely irrelevant. It is what the reading is with the boiler on that is important; but also unlikely to have changed on the service.
Without knowing what the engineer did all i can suggest is that the pump speed was turned down a bit. But also in the back of my mind i can't help thinking that there is nothing wrong and you are being paranoid.
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local