Pumps

Hi, Having a loft conversion done and have decided to install coffin tank(s) in eaves (depending on whether one or two required as not a lot of room there) and keep existing HWC (first floor bedroom) and boiler (outside in brick housing). Builder says that the loft shower and basin will need to be pumped, which I agree with. We would also like the 1st floor shower pumped too. My builder is saying in order to do this just one pump is required to be fitted but that 1st floor shower and basin as well as loft shower and basin should be pumped so both bathrooms are supplied by pump. The pressure in 1st floor is adequate for basin so I don't think there is need. Don't want pump coming on everytime taps opened in 1st floor bathroom. Builder says otherwise 2 separate pumps required is that correct? Any advice really appreciated.