No hot water in taps, but shower and WM are fine...

We are having an issue in our flat at the moment. Basically there is no hot water coming out either the kitchen or bathroom taps. It just runs cold... The shower and washing machine are absolutely fine though. We have a boiler in a bedroom and a tank in an airing cupboard. We set the panel near the tank to get the hot water to come on for 3 hours today as we thought maybe the water in the tank had all gone cold and it just needed to all heat up but it still just sends cold water to the kitchen and bathroom taps. However when the water was on but CH was off the towel heater in the bathroom was hot... Certain pipes near to the tank are red hot but others are cold. We know nothing about plumbing and the plumber the landlord sends out just keeps saying it’s fixed now but it never is fixed! We are always at work when he comes so we don’t know what he’s actually done to it. We are very frustrated and have no confidence the landlord will get this sorted. Any suggestions at this point would be great! There is a diverter valve which seems to be working fine as the lever moves accordingly