Regs: as to bazzer's comment about the water pressure, he might find that his plumber/gasfitter installed a water pressure regulator as part of the and configured it to the recommended settings. it may just be a matter of getting under the house and adjusting the inward pressure (as long as your fittings can all handle it! some new taps/mixers are *not* rated for high pressure). Of course, an XR26 is only ever going to handle up to 30 litres per minute.

I'll check it out, but I think it's really just that we had insanely good pressure before.  Now, it's being limited by the hot water system.  I'll continue monitoring the situation, and contact the gasfitter if I'm not happy.  Thanks for the advice though!