yes lots of people call engineers out to repressurise.. in most housing associationa and local authorities its now common practice to be written in the contract that tenants should niether vent rads or repressurise…
but yes folks do pay to have it done properly.
the system should be cold and the lowest rads vented first leaving the highest point usually the bathrom rad till last then re pressurise to ‘the green’ or about 1.25 bar.. DO not forget to disconect the filling loop.. water regs stipulate it should be so that the drinking water cannot be contaminated and also if the ‘tap’ is leaky water will eventually continously fill your boiler till its goes…