I moved into into a new house with my husband and all 3 mixer showers running luke warm. Get very hot water out the sink and bath taps with good pressure. But showers not hot. The only way I can get them to go hot is if I run the cold sink tap in that bathroom and then the shower goes a lovely temperature (at the expense of running cold water from other outlets). The other thing that works (oddly) is changing the shower head function to a high pressure jet which causes the temp of the shower to go from 37.2 degrees up to 41.5 degrees (a difference of 4.3) Boiler working. Heating working. I have a megaflo unvented indirect hot water cylinder upstairs where all my showers are. I repressurised the megaflow which has made no difference. No water dripping from the tundish. Plumbers have come and gone with no solution. Any solutions/thoughts/diagnosis as to what’s causing this would be greatly appreciated! I can't help but think its the megaflo. Have attached photos of bits around my megaflo at the back if that helps.