I have 'upgraded' my hot water and heating system to a combi boiler from an ecconomy 7 system?

the boiler is high up in the kitchen on the ground floor and our old water heater was high up in the bathroom (directly above the kitchen). Since the combi has been fitted the water pressure in the kitchen sink has increased dramatically however the waterpressure on the bath has decreased dramatically. I ume this is because the kitchen sink is below the boiler and the bath is above the boiler? am I right in thinking if I move the boiler to high up in the bathroom the water pressure will dramatically improve like the kitchen water pressure has? Is there an alternative to improve the bathroom water pressure? pumps?