It is possible that both your shower and radiators are weeping as a result of the change in pressure that they now have to withstand.
But be aware that the shower and its plumbing is now subject to mains water pressure. Whatever that maybe in your area (it can vary from day to day and minute to minute) the radiators should be subject to a minimum constant pressure of about 1-1.2 bar increasing when the system water in your radiators is hot but should not approach 3 bar.
I may be stating the obvious but your radiator loop and heating pipe work are entirely independant of the plumbing and water to your shower and taps.