Plumbing companies can only replace pumps and cannot repair pumps so they will naturally replace your pump even if the problem is a very small.
This could be very costly for you if you replace a Stuart Turner pump with some companies charging Astronomical charges of €1200 or more to replace a negative head pump so its worth getting a pump company who are specialists to repair your Stuart Turner pump and you may get another 10 years out of your pump. You maybe lucky to find a plumber who can repair your pump but these are rare.