I have a thermostatic controlled Mira, direct connection to hot on combi, along with cold feed, it was an expensive one, but have had no problems at all in eleven years, and still going strong. The only other problem one may have with this type of shower going hot and cold is the plate to plate heat exchanger being blocked up on the boiler its self, or the plates have closed up. No one as come back as to hot water from the tap?????