It sounds to me that the cold feed to your bath taps is direct from the mains if the pressure is so much higher than the hot. It is actually illegal to have a shower plumbed such that someone running cold water elsewhere in the house can reduce the cold water pressure and have the shower run hotter. You could have the bath taps re-plumbed such that the cold feed is from the header tank - that way both taps will have the same water pressure and you should be able to adjust the flow for a good temperature.