Margaret,
The work with respect to the shower pump is on the tank side of the system. It will have no impact whatsoever on the flow of water from the boiler to the CH/HW system.
Not being pessimistic, but in view of your installers track record, It is probable that he / she has not installed the pump and associated electrics and pipework to a professional standard.
With respect to the way forward, I would refer you to my last post.
On a serious note, if it was my house, I would not let your installer tinker any further with the installation until he /she had explained to me what the problem was and how
The work with respect to the shower pump is on the tank side of the system. It will have no impact whatsoever on the flow of water from the boiler to the CH/HW system.
Not being pessimistic, but in view of your installers track record, It is probable that he / she has not installed the pump and associated electrics and pipework to a professional standard.
With respect to the way forward, I would refer you to my last post.
On a serious note, if it was my house, I would not let your installer tinker any further with the installation until he /she had explained to me what the problem was and how